cluster/afr: Fix inode_forget assert failure

Problem:
If two self-heals are triggered on same inode in
parallel then one inode will be linked and the other
inode will not be linked as an inode with that gfid
is already linked in inode table. Calling inode-forget
on that inode leads to assert failure.

Fix:
Always use linked inode for performing self-heal.

Added inode-forgets in other places as well even though
its not really a memory leak.

Change-Id: Ib84bf080c8cb6a4243f66541ece587db28f9a052
BUG: 1091597
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/7567
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>