Repair cluster prove tests for FB environment

Summary:

Several prove tests use the 'launch_cluster' function to set up a
clustered volume. This replies on using multiple local IP
addresses, one for each server. Since IPV6 provides only ::1 as
a local address, as opposed to IPv4's complete 127.x.x.x subnet,
this cannot work in a pure IPv6 environment.

However, FB systems do at least have enough IPv4 stack to talk
locally, so fix launch_cluster to work properly when default
transport is IPv6.

To do this:

1) explicitly set transport.address-family volume option to inet in
   launch_cluster().

2) teach glusterd to honor transport.address-family when connecting
   to peer glusterds in glusterd_friend_rpc_create(). Previously
   transport.address-family was used only for binding local socket,
   not for communicating with peers.

Test Plan:

prove -f --timer ./tests/basic/glusterd/arbiter-volume-probe.t

Reviewers:

Subscribers:

Tasks:

Blame Revision:

Change-Id: I077d8549dcdbe4919ac7df34856a4b2d1428cdb6
Signed-off-by: Kevin Vigor <kvigor>
Reviewed-on: http://review.gluster.org/16225
CentOS-regression: Gluster Build System <jenkins.org>
NetBSD-regression: NetBSD Build System <jenkins.org>
Reviewed-by: Shreyas Siravara <sshreyas>
Smoke: Gluster Build System <jenkins.org>