dht/rebalance: Do not allow rebalance when gfid mismatch found

Due to race condition, it may so happen that, gfid obtained
in readdirp and gfid found by lookup are different for a given
name. in that case do no allow the rebalance.

Readdirp of an entry will bring the gfid, which will be stored
in the inode through inode_link, and when lookup is done and
gfid brought by lookup is different from the one stored in the
inode, client3_3_lookup_cbk will return ESATLE and error will be
captured by rebalance process.

Cherry picked from commit 72c7afcd:
> Change-Id: Iad839177ef9b80c1dd0e87f3406bcf4cb018e6fa
> BUG: 1104653
> Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
> Reviewed-on: http://review.gluster.org/7973
> Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
> Reviewed-by: Vijay Bellur <vbellur@redhat.com>

Also merged the oneline change from commit de22a20a:
> Change-Id: I979b7333efa93b1e8f4c73ccf048d48e308f9289
> BUG: 1104653
> Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
> Reviewed-on: http://review.gluster.org/8073
> Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
> Reviewed-by: Vijay Bellur <vbellur@redhat.com>

Change-Id: Iad839177ef9b80c1dd0e87f3406bcf4cb018e6fa
BUG: 1138922
Signed-off-by: Nithya Balachandran <nbalacha@redhat.com>
Reviewed-on: http://review.gluster.org/8712
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>