We also need to delete osr entries when deleting ArtMethod.

In the unfortunate event an ArtMethod gets allocated at the
same location as an old (deleted) ArtMethod, the osr_code_map_
lookup will succeed and return garbage. So we need to delete
entries in the osr_code_map_ when an ArtMethod gets deleted.

This should finally fix:
dalvik.system.DexClassLoaderTest#test_twoJar_diff_getResourceAsStream

Change-Id: I7c8b775c3376a6cfcb907f09b783e393967ad82d