LU-13641 socklnd: announce deprecation of 'use_tcp_bonding'

LU-13641 socklnd: announce deprecation of 'use_tcp_bonding'

Add warning to be printed if 'use_tcp_bonding' option is used
notifying the user that the feature is being deprecated.
It is suggested to use MR configuration with dynamic discovery
instead.

Multi-Rail feature doesn't need to be explicitly enabled.
To use MR instead of tcp bonding, group the interfaces
on the same network using the lnetctl utility:

	lnetctl net add --net tcp --if eth2,eth3

or via the modprobe configuration file (/etc/modprobe.d/lnet.conf
or /etc/modprobe.d/lustre.conf):

        options lnet networks="tcp(eth2,eth3)"

and make sure dynamic discovery is enabled:

        lnetctl set discovery 1

MR will aggregate the throughput of all configured and available
networks/interfaces shared between peer nodes.

Test-Parameters: trivial
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: I34288ae1c8a1c4092f88b45a571312691f145218
Reviewed-on: https://review.whamcloud.com/41088
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>