test: only set INSTANA_TRACING_DISABLE when tracing is actually disabled

ProcessControls was setting INSTANA_TRACING_DISABLE=false for all tests
where tracingEnabled=true (the default). According to the precedence rules
in disable.js, when INSTANA_TRACING_DISABLE is set to 'false', it takes
precedence over INSTANA_TRACING_DISABLE_INSTRUMENTATIONS and
INSTANA_TRACING_DISABLE_GROUPS, preventing granular disable configurations
from working in tests.

This caused logging integration tests to fail when trying to disable
specific instrumentations using INSTANA_TRACING_DISABLE_INSTRUMENTATIONS
or INSTANA_TRACING_DISABLE_GROUPS.

Changed ProcessControls to only set INSTANA_TRACING_DISABLE='true' when
tracingEnabled=false, and not set it at all when tracingEnabled=true,
allowing other disable environment variables to work correctly.

Author: aryamohanan

packages/collector/test/test_util/ProcessControls.js

@@ -151,7 +151,6 @@ class ProcessControls {
         APP_CWD: this.cwd,
         INSTANA_AGENT_PORT: agentPort,
         INSTANA_LOG_LEVEL: 'warn',
-        INSTANA_TRACING_DISABLE: !this.tracingEnabled,
         INSTANA_FORCE_TRANSMISSION_STARTING_AT: '1',
         INSTANA_FULL_METRICS_INTERNAL_IN_S: 1,
         INSTANA_FIRE_MONITORING_EVENT_DURATION_IN_MS: 500,
@@ -164,6 +163,13 @@ class ProcessControls {
       opts.env
     );
 
+    // Only set INSTANA_TRACING_DISABLE when tracing is actually disabled to avoid
+    // overriding other disable environment variables (INSTANA_TRACING_DISABLE_INSTRUMENTATIONS, etc.)
+    // See packages/core/src/config/configNormalizers/disable.js for precedence rules
+    if (!this.tracingEnabled) {
+      this.env.INSTANA_TRACING_DISABLE = 'true';
+    }
+
     if (this.usePreInit) {
       this.env.INSTANA_EARLY_INSTRUMENTATION = 'true';
     }