Hold onto FileHandles for glBindSharedBufferQCOM calls

The internal implementation of glBindSharedBuffer does not dup
the file descriptor, so to be pedantic about fd lifetime we
need to hold onto the fd until the gl buffer is deleted.

Bug: b/34256609
Test: manually switched between apps
Change-Id: I35bfbfe6a6b793bc3bdf38d7ddca31699ee0f4ff