gfs2: Fix gfs2_qa_get imbalance in gfs2_quota_hold

This patch fixes a case in which function gfs2_quota_hold encounters an
assert error and exits. The lack of gfs2_qa_put causes further problems
when the inode is evicted and the get/put count is non-zero.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>