scripts: policy-node: don't use fallback for dont-reconnect w/ target

Connecting dont-reconnect nodes that have a defined target to fallback probably does not make sense.

They will be linked to a target that the client likely did not intend, and the link will not be changed later on.

In Pulseaudio, if the defined target is not found, streams are not connected to the fallback but instead fail. This happens also with streams that don't have DONT_MOVE specified.

Pipewire-media-session also did not link dont-reconnect streams with a defined target to the fallbacks.

See https://gitlab.freedesktop.org/pipewire/media-session/-/blob/master/src/policy-node.c#L1106

See #207 (closed)