According to the ANGLE_multiview spec, glCopyTex* functions must
generate an INVALID_FRAMEBUFFER_OPERATION error if the active read
framebuffer has a multi-view layout.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: Icadc4ac79843986076594da25a90ba807e511d1e
Reviewed-on: https://chromium-review.googlesource.com/589447Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Martin Radev <mradev@nvidia.com>