MFC r320165-r320167

r320165:
devd(8): Remove pidfile on shutdown

Sponsored by: Spectra Logic Corp

r320166:
Require devd to be running for its ATF tests to run

The ATF tests communicate with the system's running devd

PR: 220169
Reported by: gjb
Sponsored by: Spectra Logic Corp

r320167:
zfsd(8): Remove pidfile on shutdown

Sponsored by: Spectra Logic Corp