Add support for opensmtp in check_mailq.
PR: 222237
Submitted by: mmokhi
Obtained from: https://github.com/nagios-plugins/nagios-plugins/commit/d56818f5121b05439c7b7a1655d96ab39e066797
Obtained from: https://github.com/monitoring-plugins/monitoring-plugins/pull/1495
Sponsored by: Absolight