glusterd: add option support for own-thread

Like enabling SSL, enabling own-thread has to be done separately for
clients and servers.

 * client.own-thread for clients (including internal like self-heal)

 * server.own-thread for servers (including e.g. glusterd)

It's very unlikely that you would ever want to set one without the
other, but they're separate anyway just in case.  Check for "private
polling thread" in the relevant logs to make sure the option took
effect, because otherwise you might not notice any difference besides
inreased performance.  ;)

Change-Id: Ifaee8de52f0b959bcdf7f6b56faeee549ee56604
BUG: 1158648
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/8931
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>