Automatic merge from submit-queue

Change minion to node

Continuation of #1111

I tried to keep this PR down to just a simple search-n-replace to keep
things simple.  I may have gone too far in some spots but its easy to
roll those back if needed - just let me know.

I avoided renaming `contrib/mesos/pkg/minion` because there's already
a `contrib/mesos/pkg/node` dir and fixing that will require a bit of work
due to a circular import chain that pops up. So I'm saving that for a
follow-on PR.
Signed-off-by: Doug Davis <dug@us.ibm.com>