LU-15137 socklnd: expect two control connections maximum

LU-15137 socklnd: expect two control connections maximum

As a result of connecting to ourselves, e.g. pinging own nid,
two control type connections are established vs. just one
in case of connecting externally.
Fix the control connection counter to be able to handle that.

Lustre-change: https://review.whamcloud.com/45461
Lustre-commit: ee9a03d8308c5918a17e2e45fd59ee5a4c38acaf

Test-Parameters: trivial testlist=sanity-lnet
Fixes: cbf740d0 ("LU-12815 socklnd: add conns_per_peer parameter")
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: Idce01d81e3924226b5b163d2472cbcd4f6eb5819
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46050
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>