improve logging

Tell in message line files that are related to error, most common being
path of the pid file that has permission issue.  The state change line is
also a little bit more readable now.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
avoid double directory indicators in pid file path

The state directory may, or may not, have in definition trailing slash
and either case needs to work the way one usually expects.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>