copr-be-dev: don't try to reach the rabbit server over ssh
    
    ... it is down on staging.  So the whole role/messaging/base is broken,
    and we can not depend on it:
    
    TASK [rabbit/user : Create the user in RabbitMQ] ***********************
    Tuesday 11 August 2020  05:37:34 +0000 (0:00:00.121)       0:05:22.244 *
    Tuesday 11 August 2020  05:37:34 +0000 (0:00:00.121)       0:05:22.243 *
    [WARNING]: Unhandled error in Python interpreter discovery for host
    rabbitmq01.stg.iad2.fedoraproject.org: Failed to connect to the host via
    ssh: ssh: connect to host rabbitmq01.stg.iad2.fedoraproject.org port 22:
    Connection timed out
    fatal: [copr-be-dev.aws.fedoraproject.org]: UNREACHABLE! => {"changed":
    false, "msg": "Data could not be sent to remote host
    \"rabbitmq01.stg.iad2.fedoraproject.org\". Make sure this host can be
    reached over ssh: ssh: connect to host rab
    bitmq01.stg.iad2.fedoraproject.org port 22: Connection timed out\r\n",
    "unreachable": true}
    
    So there's now a new toggle named "copr_messaging", turned on only for
    production copr instance.