Disable RCMDS by default.
This was announced in this thread:
https://lists.freebsd.org/pipermail/freebsd-arch/2017-June/018239.html
Applying plan proposed by ngie@ in:
https://lists.freebsd.org/pipermail/freebsd-arch/2017-June/018249.html
The port has been submitted as net/bsdrcmds in r444814.
Approved by: bapt, roberto, and others