LU-12569 o2iblnd: Make credits hiw connection aware

LU-12569 o2iblnd: Make credits hiw connection aware

The IBLND_CREDITS_HIGHWATER mark check currently looks only
at the global peer credits tunable, ignoring the connection
specific queue depth when determining the threshold at
which to send a NOOP message to return credits.

This is incorrect because while connection queue depth
defaults to the same as peer credits, it can be less than
that global value for specific connections.

So we must check for this case when setting the threshold.

Test-Parameter: nettype=o2ib
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ie028ae11cdbd0f75a38b265b7ab5830f92f08d90
Reviewed-on: https://review.whamcloud.com/35578
Reviewed-by: Chris Horn <hornc@cray.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>