LU-13255 gnilnd: Use wait_var_event_warning()

LU-13255 gnilnd: Use wait_var_event_warning()

LNet has a recurring pattern of waiting for some variable to
reach a particular value, and generating a warning every second that
it hasn't.  In many cases the warning has a higher priority if the
wait has been for a power-of-2 seconds.

This pattern is now  embodied in
  wait_var_event_warning()

Use that macro in various places in gnilnd.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I7be82a175c7b1b8da4df99199378e7af5328e0e7
Reviewed-on: https://review.whamcloud.com/37594
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>