Fix product_services apps getting PRODUCT scanFlags.

Make all comparisons using startsWith for partition checks more
robust by appending a forward flash.

Also add a test.

Bug: 80741439
Test: atest FrameworksServicesTests:PackageManagerServiceTest
Change-Id: Ibe085d0edec44bf8b49f313209f9aec22b70aec1
2 files changed