glusterfsd: Round robin DNS should not be relied upon with
config service availability for clients.

Backupvolfile server as it stands is slow and prone to errors
with mount script and its combination with RRDNS. Instead in
theory it should use all the available nodes in 'trusted pool'
by default (Right now we don't have a mechanism in place for
this)

Nevertheless this patch provides a scenario where a list of
volfile-server can be provided on command as shown below

-----------------------------------------------------------------
$ glusterfs -s server1 .. -s serverN --volfile-id=<volname> \
      <mount_point>
-----------------------------------------------------------------
                   OR
-----------------------------------------------------------------
$ mount -t glusterfs -obackup-volfile-servers=<server2>: \
      <server3>:...:<serverN> <server1>:/<volname> <mount_point>
-----------------------------------------------------------------

Here ':' is used as a separator for mount script parsing

Now these will be remembered and recursively attempted for
fetching vol-file until exhausted. This would ensure that the
clients get 'volume' configs in a consistent manner avoiding the
need to poll through RRDNS.

Change-Id: If808bb8a52e6034c61574cdae3ac4e7e83513a40
BUG: 986429
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/5400
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>