glusterd: Add a cmd for getting uuid of local node

Usage: gluster system:: uuid get

This is needed since we generate uuid of a node in a lazy manner. ie, we
generate a uuid for the node only on the first volume or peer operation,
when the node needs an external identity.  With this command, we can
force[1] the uuid generation, without a volume or peer operation performed.

[1]: Querying for uuid (or uuid get), forces uuid to come into
existence.

Change-Id: I62c8b6754117756aa4d773dd48af4ddeb1a1d878
BUG: 971661
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/5175
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>
cluster/dht: Make sure loc has gfid

Problem:
In some code paths neither loc->gfid nor loc->inode->gfid
is populated which leads to EINVAL for linkfile setattr
in dht_linkfile_attr_heal.

Fix:
Populate loc->gfid before dht_linkfile_attr_heal.

Change-Id: I062770e6f6eaead304eff1dae81f8588a3b97eed
BUG: 971805
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5178
Reviewed-by: Shishir Gowda <sgowda@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>