Accept Quantums rootwrap.conf in etc/quantum/rootwrap.conf

As part of the review request
https://review.openstack.org/#/c/24615/
the Quantum rootwrap.conf is moving to etc/quantum subdir.
Prefer the new location.

Change-Id: I2a893c7b21e252543372854ba511f61cd1fde02f
Merge "Accept Quantums rootwrap.conf in etc/quantum/rootwrap.conf"