LU-16461 kfilnd: Modify peer credits and RX buffers

LU-16461 kfilnd: Modify peer credits and RX buffers

It's desirable to lower peer credits because smaller values allow us
to cancel outstanding traffic to down peers faster (because there is
less traffic in flight). Testing shows that peer_credits 16 does not
perform any worse than our current default. Let's make 16 the
new default.

In addition, testing shows a benefit for further increasing the
default number of immediate receive buffers. Increase this to 8.

HPE-bug-id: LUS-11421
Test-Parameters: trivial
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I877fe408b276071f33a99c8b3b50d13f597aaa29
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49592
Reviewed-by: Ron Gredvig <ron.gredvig@hpe.com>
Reviewed-by: Ian Ziemba <ian.ziemba@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>