LU-14979 lnet: set max recovery interval duration

LU-14979 lnet: set max recovery interval duration

Add a tunable parameter to limit the recovery ping interval which was
previously statically set to 900.
This can be done by using:

  lnetctl set max_recovery_ping_interval <value>

Modify sanity-lnet test 210/211 to validate this new functionality.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Cyril Bordage <cbordage@whamcloud.com>
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I766ceb6e03ffdab125005e16472b6f9eeadfb9d5
Reviewed-on: https://review.whamcloud.com/44927
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>