create .rabbitmqadmin.conf for rabbitmq_exchange provider

Commit 7f5a21f introduced configuring of SSL for the rabbitmq web management UI. This broken any providers which used `rabbitmqadmin` as they had no way of knowing what port to connect to (by default it connects to port 15672) or if it needed SSL. This pull request creates `/tmp/.rabbitmqadmin.conf` as the provider sets `$HOME` to be `/tmp` as `rabbitmqadmin` checks for its `.rabbitmqadmin.conf` in `$HOME/.rabbitmqadmin.conf`.