Remove unnecessary script stanza from Upstart config.

We don't need to spawn a shell just to run a binary
Remove incorrect ‘expect fork’ stanza from Upstart config.

We don't actually fork() when called with --no-daemon, so telling Upstart
to expect a fork will cause it to fail to track our process state correctly
Enable dbus support when running from Upstart
Simplify Upstart start-on condition

DBus can't be started before local filesystems are ready, so omit the
explicit dependency on local-filesystems