It is sufficient to use /bin/sh in vm_cleanup.sh script.
Do not hardfail if the removal of globaleaks configuration is fucked up.

In postrm maintainer script, we attempt to remove globaleaks configuration from
/etc/tor/torrc. There are many reason why this may fail:
* User might be stupid
* Tor might be not present
So here I am just telling dpkg to proceed anyway if something fails. This will
be supposedly be solved once we fix #70 (KEEP IN MIND #962!)