Add AMS lock protection to mAppsInBackgroundRestricted collection

When the process is started asynchronously, the mAppsInBackgroundRestricted collection lacks AMS lock
protection and will throw ConcurrentModificationException
crash with a low probability.

Bug: 236582924
Test: Treehugger
Change-Id: Ieec1de9ee1fd336cf1de54566f80442e3cd3acdd
1 file changed