Add information on op-version for clients to volume status output

[samikshan]

Currently the gluster volume status <VOLNAME|all> clients command gives us the following information on clients:

1. Brick name
2. Client count for each brick
3. hostname:port for each client
4. Bytes read and written for each client

Information regarding the maximum op-version that each client supports should be added to the volume status command so that users can get the op-versions supported by each client in one command.

Corresponding bug: https://bugzilla.redhat.com/show_bug.cgi?id=1409078

[atinmu]

Patch http://review.gluster.org/16303 is now in mainline.

[ShyamsundarR]

Part of release-3.10 as well