run: use portable shell

Nothing in run required bash, except for the shebang.  On systems
where /bin/bash doesn't exist (I hit it on FreeBSD), using /bin/sh
instead fixes a 'make check' failure:
gmake[3]: Entering directory `/usr/home/dummy/libvirt/python'
  GEN    check-local
/usr/local/bin/bash: ../run: /bin/bash: bad interpreter: No such file or directory

* run.in: Use /bin/sh, not bash.

run.in

@@ -1,6 +1,6 @@
-#!/bin/bash -
+#!/bin/sh
 # libvirt 'run' programs locally script
-# Copyright (C) 2012 Red Hat, Inc.
+# Copyright (C) 2012-2013 Red Hat, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by