Update to support npf as AUTO but not starting it.

Summary: Per BOUNDARY-3245, I've added a new cmdline switch (/NPFSTARTUP=AUTO) which will set the npf driver to start on system boot (i.e. AUTO) but not start it up at that moment.

Test Plan: Make sure it does that thing it should do.

Reviewers: busterb, thirty8super

Differential Revision: http://phabricator.cid1.boundary.com/D2297