make AMQP support when develop_mode=false

When develop_mode=false, the password of mq user "guest"
in the databag user_passwords is required. But the current
code doesn't support. I made it work, and add the test cases.

Closes-Bug: #1257554
Change-Id: I0d01bd73eaec9cc90304e67484fec15fad061504
Merge "make AMQP support when develop_mode=false"