lib/monitor.rb: prevent to initialize MonitorMixin twice
Suggested by Benoit Daloze. [ruby-core:88504] [Feature #15000]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65822 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
lib/monitor.rb: prevent to initialize MonitorMixin twice
Suggested by Benoit Daloze. [ruby-core:88504] [Feature #15000]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65822 b2dd03c8-39d4-4d8f-98ff-823fe69b080e