Reuse existing Background Thread in AppFunctionPackageMonitor

https://android-build.corp.google.com/abtd/run/L18200030012141384/

Bug: 417277423
Test: Boot time test
Flag: EXEMPT simple bugfix.
Change-Id: I242b47b1dc9c3f181bfe1f48aaee72bbc806d177
1 file changed