With the new oslo-privsep library, there is now a
privsep-helper command that is used to escalate
privledges.
This command needs to be runnable by the neutron user
via sudo without a password. The old rootwrap command
is still used as well, so for now we need to have
both.
Change-Id: I8e9743da3e51e71a113d958c22007cf54aa17fc4