sf: Always use opengles for screen capture

Go back to the usage of GRALLOC_USAGE_HW_TEXTURE and GRALLOC_USAGE_HW_RENDERER
in captureScreenImplLocked regardless of useReadPixels value

This fixes the EGL_NO_IMAGE_KHR error returned from
eglCreateImageKHR (blank images returned from screenshot path)

Change-Id: I62fe90a081607b9e89c67f3dcfd34c84efc89d35
libs/gui: Release acquired buffer when createImage fails

When EGL fails to create an KHR image for an acquired buffer,
release the buffer before returning with error. This unblocks
the dequeue buffer call waiting and may succeed in the next queue.

CRs-Fixed: 624244

Change-Id: I674807f4bb1f1253cb787daaa5a7adf351caaae7
(cherry picked from commit 9e9b12d7f37a6120a705db56a4374e7141c79a41)