mesa: check framebuffer completeness only after state update

The change made in 88d66583 ("mesa: check draw buffer completeness
on glClearBufferfi/glClearBufferiv") correctly updated the state prior
to checking the framebuffer completeness on glClearBufferiv but not in
glClearBufferfi.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Fixes: 88d66583 ("mesa: check draw buffer completeness on glClearBufferfi/glClearBufferiv")
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2072
(cherry picked from commit f93bb903)