mount.glusterfs: getopts support and cleanup

This patch is an attempt to provide some much needed
cleanup for future maintenance of `mount.glusterfs`

- Add checks for command failures
- Spliting large code into subsequent simpler functions
- Standardized variables
- use 'bash' instead of 'sh' - since string manipulation
  and variable handling is far superior
- Overall code cleanup and Copyright change to Red, Hat Inc.
- Add new style of mounting with a comma separated list
  ~~~
  $ mount -t glusterfs <IP1/HOSTNAME1>,<IP2/HOSTNAME2>,..<IPN/HOSTNAMEN>:/<VOLUME> <MNT>
  ~~~
- Update age old `manpage` with new options :-)

Change-Id: I294e4d078a067d67d9a67eb8dde5eb2634cc0e45
BUG: 1040348
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/5931
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Amar Tumballi <amarts@gmail.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>