check-rabbitmq-amqp-alive: properly close connection if connected
check-rabbitmq-amqp-alive: properly close connection if connected

Closes #38
EslamElHusseiny/sensu-plugins-rabbitmq,alexpekurovsky/sensu-plugins-rabbitmq,sensu-plugins/sensu-plugins-rabbitmq,DvaBearqLoza/sensu-plugins-rabbitmq