Move rootwrap filters definition from being defined within Nova
code to being defined in configuration files to facilitate pluging-in
new rootwrap commands.
Transition notes:
* nova-rootwrap now requires an additional (first) parameter pointing
to the root-owned rootwrap.conf file, sudoers needs to be updated
to specify that ("nova-rootwrap /etc/nova/rootwrap.conf *")
* Packagers should ship {compute,network,volume}.filters inside a
directory listed in rootwrap.conf rather than shipping
nova/rootwrap/{compute,network,volume}.py
* Filter definitions now only support strings. The KillFilter (which was
using arrays as parameters) was modified and the tests updated.
Implements bp nova-rootwrap-pluggable-filters
Corresponding devstack change needs to land first, so that tests pass:
https://review.openstack.org/8842
Change-Id: I2350154cd8057bd57926ed542de035626f7de37d
9cb89c317f