LU-12452 socklnd: allow setting IP ToS value

LU-12452 socklnd: allow setting IP ToS value

This patch add a new tuning to set the IP "Type of Service" value for
TCP QoS.

It adds the module parameter "tos":
...
options ksocklnd tos=106

tos=-1 means "disable": the LND will not try to set the ToS value.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Etienne AUJAMES <eaujames@ddn.com>
Change-Id: I15d3d1dfb645cc778763713c5018f66bea8567c6
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54080
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>