cluster/afr: Fixed mem leaks in self-heal code path.

	backport of: http://review.gluster.org/8821

AFR_STACK_RESET previously didn't cleanup afr_local_t,
leading to memory leaks. With this patch, cleanup is
done.

All credit goes to Pranith Kumar Karampuri.

Change-Id: I26506dfd9273b917eff5127c3e0cf9421e60f228
BUG: 1145914
Reviewed-on: http://review.gluster.org/8831
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>