Fix bugs in image.create tests and clean up code a bit

 * Cube map tests were incorrectly using EGL image target as format.

 * GL_R & GL_RG cases weren't properly checking for extensions due
to typo in m_format initialization.

 * General cleanup for format/internalFormat handling and separation.

Change-Id: I6c1b28385269d4af60d1a5e097ef1dbb11413f6b
3 files changed