glusterd: Disable ping-timer between glusterd and brick process

When there are too many IO happening, brick process epoll thread
will be busy and fails to respond to the glusterd pick packet within
30sec.
Also epoll thread can be blocked by a big-lock.

Solution is to disable ping-timer by default and only enable where ever
required

Later when the epoll thread model changed and made lighter,
we need to revert back this change. http://review.gluster.com/3842 is
one such approach.

Change-Id: I7f80ad3eb00f7d9c4d4527305932f7cf4920e73f
BUG: 1097224
Signed-off-by: Vijaikumar M <vmallika@redhat.com>
Reviewed-on: http://review.gluster.org/7753
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>