libhwui: Fix a native crash with patch caching

This commit makes the system silently deal with requests to remove
patches that have already been tagged for removal instead of dumping.
The garbage collector method (PatchCache::clearGarbage) should deal
with getting rid of this patch at a later date regardless since it
has already been added to the garbage array.

Fixes AOSPA-835.

Change-Id: I9bd801926bc5de5cdb0324c9ddeb91bd8bbfe155
Merge "libhwui: Fix a native crash with patch caching" into kitkat