glusterd: statedump support

Although glusterd currently has statedump support but it doesn't dump its
context information. Implementing glusterd_dump_priv function to export per-node
glusterd information would be useful for debugging bugs. Once implemented, we
could enhance sos-report to fetch this information. This would potentially
reduce our time to root cause and data needed for debugability can be dumped
gradually.

Following is the main items of the dump list targeted in this patch :

    * Supported max/min op-version and current op-version
    * Information about peer list
    * Information about peer list involved while a transaction is going on
      (xaction_peers)
    * option dictionary in glusterd_conf_t
    * mgmt_v3_lock in glusterd_conf_t
    * List of connected clients
    * uuid of glusterd
    * A section of rpc related information like live connections and their
      statistics

There are couple of issues which were found during implementation and testing
phase:
 - xaction_peers of glusterd_conf_t was not initialized in init because of which
   traversing through this list head was crashing when there was no active
   transaction
 - gf_free was not setting the typestr to NULL if the the alloc count becomes 0
   for a mem-type earlier allocated.

Change-Id: Ic9bce2d57682fc1771cd2bc6af0b7316ecbc761f
BUG: 1139682
Signed-off-by: Atin Mukherjee <amukherj@redhat.com>
Reviewed-on: http://review.gluster.org/8665
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>