Fix RootsCache invalidation bugs.

When RootsCache is still running and it detects a provider/package
change, it needs to force reload roots.  Also fix cache invalidation
bug in ContentService to allow for Uri prefix matches.

Mark internal storage broadcasts with flag to bypass new background
checks.

Bug: 27759529
Change-Id: I9d9c6fe15d8640ff56ae7214afb3bac673682c28