add support for KEYBASE_SYSTEMD to run_keybase
add support for KEYBASE_SYSTEMD to run_keybase

This is a substantial rewrite that compartmentalizes everything a little
better.

keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client