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.

Change-Id: Iad839177ef9b80c1dd0e87f3406bcf4cb018e6fa
BUG: 1139984
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>
Reviewed-on: http://review.gluster.org/8670
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>