rebalance: ``check_free_space`` should ignore quota_statfs

quota_statfs() returns aggregated details of space usage
of bricks this causes distribute to be confused during
``rebalance``, where ``statfs()`` values are used to
schedule file migration.

We can make sure the values of ``statfs`` are from
individual bricks by selectively instructing
``quota_statfs()`` to return non aggregated values.

Change-Id: I1397faeee66a1b9c26709cfda693286d227a4170
BUG: 1158262
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/8996
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: N Balachandran <nbalacha@redhat.com>
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>