LU-6002 lnet: startup acceptor thread dynamically

LU-6002 lnet: startup acceptor thread dynamically

With DLC it's possible to start up a system with no NIs that require
the acceptor thread, and thus it won't start.  Later on the user
can add an NI that requires the acceptor thread to start, it is
then necessary to start it up.

If the user removes a NI and as a result there are no more
NIs that require the acceptor thread then it should be stopped.
This patch adds logic in the dynamically adding and removing NIs
code to ensure the above logic is implemented.

Signed-off-by: Amir Shehata <amir.shehata@intel.com>
Change-Id: Iecada597d417dcb8991e9fb98f6844382295246a
Reviewed-on: http://review.whamcloud.com/13010
Tested-by: Jenkins
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>