set default user to run rabbitmq cmds to user that running salt-minion

fix #17226
Revert "default run as root user because ``erlexec`` needs HOME env to be set"

This reverts commit ce91c65a7766fe784f9f87a9be59e47d7551e813.

Already set default user to run rabbitmq cmds at rabbitmq module. This
allow user to use arbitrary user to run those cmds but still has a
default that work.
add runas parameter for all functions
pep8