mesa: check draw buffer completeness on glClearBufferfi/glClearBufferiv

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 88d66583)