GFS2: Fix a use-after-free that coverity spotted

In function gfs2_inplace_release it was trying to unlock a gfs2_holder
structure associated with a reservation, after said reservation was
freed. The problem is that the statements have the wrong order.
This patch corrects the order so that the reservation is freed after
the gfs2_holder is unlocked.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>