The valectl(4) program is used to manage vale(4) switches.
Add it to the system commands so that it can be used right away.
This program was previously called vale-ctl, and stored in
tools/tools/netmap
Reviewed by: hrs, bcr, lwhsu, kevans
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D22146
