ser_mysql.sh: Switch to /bin/bash

The ser_mysql.sh script is probably not POSIX clean and currently does
not work with dash (the new default interpreter for /bin/sh in debian).

Switch back to /bin/bash, this makes the script work again across
distributions.

scripts/mysql/sip-router_mysql.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 # $Id$
 #