Fix: EXIT trap exit code propagation on bash 5.1

The openstack cron job (builder-openstack-cron) has been failing
consistently since the build-node migration from CentOS 8 (bash 4.4)
to Ubuntu 22.04 (bash 5.1) in releng/builder commit f601068e8
(Chore: Replace CentOS build-node refs with Ubuntu).

Problem:
  The cron job runs 7 cleanup scripts sequentially via conditional
  build steps: k8s clusters, stacks, servers, ports, volumes,
  image-protect, and image-cleanup. After the migration, the build
  consistently failed at the ports cleanup step with:

    No orphaned ports to process.
    Build step 'Conditional step (single)' marked build as failure

  All subsequent steps (volumes, image-protect, image-cleanup) were
  skipped due to the BuildStepRunner$Fail runner aborting the build.

Root Cause:
  Bash 5.1 (shipped with Ubuntu 22.04) has a known behavior where
  when 'set -e' (errexit) is active, a failing command inside an
  EXIT trap causes the trap's non-zero exit code to propagate as
  the script's final exit code, overriding an explicit 'exit 0'.

  The _rmtemp() EXIT trap function used this pattern:

    _rmtemp() {
        if [ -f "$tmpfile" ]; then
            rm -f "$tmpfile"
        fi
    }

  When the temp file does not exist (normal case after cleanup),
  the 'if [ -f ]' test returns false, making the if-statement's
  exit code 1. Bash 5.1 with 'set -e' propagates this as the
  script's final exit code, causing Jenkins to see a non-zero
  return and marking the build step as FAILURE.

  Bash 4.4 (CentOS 8) does not exhibit this behavior — it
  preserves the original 'exit 0' regardless of trap exit codes,
  which is why the job worked before the migration.

  This only affected scripts with 'set -eu -o pipefail':
  - openstack-cleanup-orphaned-ports.sh      (set -eu -o pipefail)
  - openstack-cleanup-orphaned-objects.sh     (set -eu -o pipefail)

  Scripts without 'set -e' were unaffected:
  - openstack-cleanup-orphaned-k8s-clusters.sh  (no set -e)
  - openstack-cleanup-orphaned-stacks.sh         (set -x only)
  - openstack-cleanup-orphaned-servers.sh         (no set -e)

  This explains why the cron job always failed at the ports step
  (the first script in the sequence with 'set -eu').

Fix:
  Replace the 'if [ -f ] / rm' pattern with 'rm -f || true' to
  ensure the EXIT trap always returns exit code 0 regardless of
  whether the temp file exists. The 'rm -f' flag already suppresses
  errors for non-existent files, and '|| true' provides a safety
  net for any unexpected failures. Stderr is redirected to /dev/null
  to suppress any spurious error messages.

Investigation:
  - Build 77811 (PASS): ran on prd-centos8-builder-2c-2g (bash 4.4)
  - Build 77812 (FAIL): first build on prd-ubuntu2204-builder-2c-2g
    (bash 5.1) after the CentOS-to-Ubuntu migration
  - All builds from 77812 to 77971+ consistently fail at ports step
  - Confirmed via S3 console logs comparison and binary search

References:
  - https://stackoverflow.com/questions/41619629
  - https://unix.stackexchange.com/questions/667368

Issue: RELENG-5951
Change-Id: Id09def17f0dbdbabebea0f96b8ef9ebc43778f93
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>

Author: askb

releasenotes/notes/fix-cron-trap-exit-code-bash51-9b3c7d216ecce5a3.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    Fix openstack cron job EXIT trap causing false build failures on
+    bash 5.1 (Ubuntu 22.04). When ``set -e`` is active and a command
+    in the EXIT trap returns non-zero, bash 5.1 propagates the trap's
+    failure exit code instead of preserving the original ``exit 0``.
+    The ``_rmtemp`` trap used an ``if [ -f ]`` pattern that returned
+    exit code 1 when the temp file didn't exist, causing the cron job
+    to fail despite all cleanup scripts completing successfully.
+    Changed to ``rm -f || true`` to ensure the trap always returns 0.

shell/openstack-cleanup-orphaned-objects.sh

@@ -72,10 +72,8 @@ _cleanup()
 
 _rmtemp()
 {
-    if [ -f "$tmpfile" ]; then
-        # Removes temporary file on script exit
-        rm -f "$tmpfile"
-    fi
+    # Removes temporary file on script exit
+    rm -f "$tmpfile" 2>/dev/null || true
 }
 
 trap _rmtemp EXIT

shell/openstack-cleanup-orphaned-ports.sh

@@ -57,10 +57,8 @@ _cleanup()
 
 _rmtemp()
 {
-    if [ -f "$tmpfile" ]; then
-        # Removes temporary file on script exit
-        rm -f "$tmpfile"
-    fi
+    # Removes temporary file on script exit
+    rm -f "$tmpfile" 2>/dev/null || true
 }
 
 trap _rmtemp EXIT