LU-7734 lnet: automatic sizing of router pinger buffers

LU-7734 lnet: automatic sizing of router pinger buffers

The router pinger uses fixed-size buffers to receive the data
returned by a ping. When a router has more than 16 interfaces
(including loopback) this means the data for some interfaces
is dropped.

Detect this situation, and track the number of remote NIs in
the lnet_rc_data_t structure.  lnet_create_rc_data_locked()
becomes lnet_update_rc_data_locked(), and modified to replace
an existing ping buffer if one is present. It is now also
called by lnet_ping_router_locked() when the existing ping
buffer is too small.

Test-Parameters: trivial
Signed-off-by: Olaf Weber <olaf@sgi.com>
Change-Id: I9474e2e162d2facdf571fe207dea254dd3f8e469