features/quota: Send the immediate parent with limit in quota statfs adjustment

Problem:
Assume the directory structure /quota_limit_dir/subdir and quota_limit_dir is
set with some limit. When quota-deem-statfs is enabled the output of
'df /quota_limit_dir' would display quota modified values wrt to
quota_limit_dir where as 'df /quota_limit_subdir/subdir' would display the
quota modified values wrt volume root (/).

This behaviour is not expected since, when mounted with subdirectory admin
doesn't want users to know information above the subdirectory mounted.

Solution:
Any subdirectory within a quota_limit_dir would show the modified values as in
the /quota_limit_dir. It searches for the nearest parent that has quota limit
set and modifies the statvfs wrt that.

Change-Id: Ie10fae8999bddbb766b1dbeb881723ed80dce688
BUG: 1080296
Signed-off-by: Varun Shastry <vshastry@redhat.com>
Reviewed-on: http://review.gluster.org/7330
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Tested-by: Raghavendra G <rgowdapp@redhat.com>