goldfish-opengl: Protect shared texture objects map

This fixes a crash in libOpenglCodecCommon by protecting
the shared texture objects map with a ReadWriteLock.

BUG=213574323
TEST=dEQP-EGL.functional.sharing.gles2.multithread.*

Change-Id: I61f9fe3c3892c3c482cee7893526f5de854b1c4d
3 files changed