Avoid unnecessary use of rootwrap for some network commands

Every time we run something as root with rootwrap, it takes about
ten times longer (setup-wise anyway). For things that don't need
to be run as root, we should avoid this hit. Nova network does
this a lot and is also slow enough to cause trouble, so this
patch attempts to address that for a few situations.

Related-bug: #1257626

Change-Id: Idc26776bf96ccfd9f50383e9d40aa47397d4e2cf
Merge "Avoid unnecessary use of rootwrap for some network commands"