Fix inverted release-EGLContext-on-pause logic.

This works around a bug in the
"Q3Dimension MSM7500" driver. That driver only
supports a single active EGLContext, so we must
release and restore the EGLContext when pausing
and unpausing.

Unfortunately the test for deciding whether to
release the context was inverted. We were
releasing the context on every device besides
the MSM7500 devices, which was a performance
drain, and we were not releasing the context on
the MSM7500, which meant the underlying driver
bug was not worked around.

Now we release the EGL context when pausing only
on the devices that have the bug.