bluetooth: don't send unsolicted replies to the endpoint Release() call

bluetooth: don't send unsolicted replies to the endpoint Release() call

It was reported that PulseAudio causes error messages in syslog from
dbus-daemon:

Jan 14 04:51:32 gentoo dbus-daemon[2492]: [system] Rejected send message, 2 matched rules; type="error", sender=":1.15" (uid=1000 pid=2864 comm="/usr/bin/pulseaudio --start --log-target=syslog ") interface="(unset)" member="(unset)" error name="org.bluez.MediaEndpoint1.Error.NotImplemented" requested_reply="0" destination=":1.1" (uid=0 pid=2670 comm="/usr/libexec/bluetooth/bluetoothd ")

The default policy on the system bus is to not let any method call
replies through if they have not been requested, and apparently
bluetoothd doesn't want replies to the Release() call.

This also changes the reply type from error to normal reply. The "not
implemented" error didn't make sense to me. We don't do any cleanup in
the Release() handler, probably because there's nothing to do. If there
is some cleanup that we should do, then it's a serious bug not to do it.

BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=104646