tests: spurious failure fix for quota-anon-fd-nfs.t

Cherry picked from commit 463d3e379d63e37764bc190be6c2f790769bea58:
> Change-Id: I4f7ee68c514d8d322e25cf74167f288a8b6f8164
> BUG: 1163543
> Signed-off-by: Atin Mukherjee <amukherj@redhat.com>
> Reviewed-on: http://review.gluster.org/9108
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Niels de Vos <ndevos@redhat.com>

Also include the usage() function in the test, and some other
improvements introduced with commit 27628b7b.

BUG: 1168173
Change-Id: I4153af903178893361157af2ab06ce4989dd849b
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/9200
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>