daemon: kill: use log level to "warn" if container doesn't exit in time
I noticed this log being logged as an error, but the kill logic actually
proceeds after this (doing a "direct" kill instead). While usually containers
are expected to be exiting within the given timeout, I don't think this
needs to be logged as an error (an error is returned after we fail to
kill the container).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>