The previous assumption that any target with "device.intended-roles"
should be managed by the role-based policy is wrong, as for example
Bluetooth SCO nodes always have "device.intended-roles = Communication"
and some ALSA devices managed by ACP also do. This is meant to be used
as a hint for the desktop policy (it's been there in PulseAudio as well)
and does not necessarily mean that a role-priority-based policy should
be applied on all links to those devices.

Instead, use a new property to explicitly mark all the targets that
are meant to be managed by the role-based policy and respect that in
all places where we check for a potential role-based policy link.

Fixes: #682