Use [[ .. ]] for test using globs

Fixes the following shellcheck error:

    SC2081 (error): [ .. ] can't match globs. Use a case statement.

https://www.shellcheck.net/wiki/SC2081

Author: mandre

test/scripts/rpm-ostree_mock

@@ -1,11 +1,11 @@
-#!/usr/bin/sh -x
+#!/usr/bin/bash -x
 
 # This script is meant to be a mock for `rpm-ostree`
 
 # Write invocation with arguments to a file to allow making assertion.
 echo "$*" >> /rpm-ostree_calls
 
-if [ "$*" != *"--append"* ]
+if [[ "$*" != *"--append"* ]]
 then
     # Caller is trying to read kernel arguments.
     cat /proc/cmdline