cluster/afr: Allow data/entry self heal for metadata split-brain

Problem:
Currently whenever there is metadata split-brain, a variable
sh->op_failed is set to 1 to denote that self heal got failed.
But if we proceed for data self heal, even code-path of data
self heal also relies on the sh->op_failed variable. So if will
check for sh->op_failed variable and will eventually fails to
do data self heal. So needed a mechanism to allow data self heal
even if metadata is in split brain.

Fix:
Some data structure revamp is done in
http://review.gluster.com/#/c/5106/ fix and this patch is
based on the above fix. Now we can store which particular self-heal
got failed i.e GFID_OR_MISSING_ENTRY_SELF_HEAL, METADATA, DATA,
ENTRY. And we can do two types of self heal failure check.
1. Individual type check: We can check which among all four
   (Metadata, Data, Gfid or missing entry, entry self heal)
   got failed.

2. In afr_self_heal_completion_cbk, we need to make check
   based on the fact that if any specific self heal got failed treat
   the complete self heal as failure so that it will populate
   corresponding circular buffer of event history accordingly.

Change-Id: Icb91e513bcc752386fc8a78812405cfabe5cac2d
BUG: 977797
Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
Reviewed-on: http://review.gluster.org/5253
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>