The patch fixes an unexposed bug in FramebufferGL which would pass
an incorrect multi-view state to StateManagerGL on texture detachment.
The bug is not exposed because upon a subsequent syncing step the
correct state is queried and restored from the framebuffer state.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: Ie0e783c53e87497b3673ef87ab9c53c3c04054a7
Reviewed-on: https://chromium-review.googlesource.com/636369
Commit-Queue: Martin Radev <mradev@nvidia.com>
Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>