cluster/dht: Allow non-local clients to function with nufa volumes.

nufa fails to init if a local brick is not found as of today.
With this patch, if a local brick is not found, nufa switches
over to dht mode of operations.

Change-Id: I50ac1af37621b1e776c8c00a772b8e3dfb3691df
BUG: 980838
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5414
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>