LU-12815 socklnd: set conns_per_peer based on link speed

LU-12815 socklnd: set conns_per_peer based on link speed

Specifying conns_per_peer=0 for a ni is now used to set
the conns_per_peer as a function of the corresponding link speed
as follows:
	conns_per_peer = (ilog2(Gbps) / 2 + 1)

Listed below are the resulting defaults for common link speeds:
	100Gbps, 200Gbps -> 4
        50Gbps		 -> 3
        5Gbps, 10Gbps	 -> 2
        less than 4Gbps  -> 1

Lustre-change: https://review.whamcloud.com/44417
Lustre-commit: c44afcfb72a1c2fd8392bfab3143c3835b146be6

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: Ief2b33a796c180d8669bd5796b3e35ec748423a5
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/45742
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>