Correctly handle unsupported OMX color format

MediaServer was caught in an infinite loop at OMX::getParameter.

OMX::getParameter returns status_t, using OMX_ErrorNoMore to loop
until the index passes beyond the last supported format
will not work since this function only returns ERROR_UNSUPPORTED.

Change-Id: Idde94a46af24641c0e5f1db909335db4c7e2b7f7