Use /bin/sh for rabbitmq-script-wrapper, not /bin/bash

There's nothing in it that is an obvious dependency on bash, and some
testing with dash as /bin/sh doesn't reveal any problems.  Neither
does checkbashisms.

Author: dpw

packaging/common/rabbitmq-script-wrapper

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # Escape spaces and quotes, because shell is revolting.
 for arg in "$@" ; do
 	# Escape quotes in parameters, so that they're passed through cleanly.