Refactored RabbitMQ.py and scripts

* devide script on functions
* suppressed html output from rabbitmq management context
* handle mgmt port via querying rabbitmq management contexts before any actions like create or delete
* add -rabbitmq_host and -rabbitmq_port instead of -rabbitmq_url
* add install of murano-api & murano-engine in murano-dashboard-integration-tests.sh after murano-dashboard
This changes allow RabbitMQ.py automatically reconnects to management port of the rabbitmq server as for previous as for current stable version.
Function check_mgmt_ctx_port() inside RabbitMQ.py handle this situation.

Also add clean install of the murano-api[engine] after murano-dashboard resolves conflict problems with python and system(yum) packages on CentOS installation.

Change-Id: I27259500efb18ea7e9a63ce60920af5824ffbd48