The use of the pseudo-blocking D-Bus calls leads to the problem that
NameLost signals are received after the reply to ReleaseName().
The problem with this is that a later acquisition of the same audio
device can potentially receive the NameLost signal corresponding to
the previous instance, due to the fact that the signal hasn't been
popped from the D-Bus message queue.
The simplest approach to solve this problem is to poll the actual name
owner from the D-Bus daemon, in order to make sure that we did really
lose the name.
The proposal uses a blocking call to GetNameOwner to avoid incosistent
states in the internal APIs: it would otherwise be possible to have a
"busy" device before the reservation has been lost, in the unlikely
case if some other process acquires the name before we got the
confirmation that the NameLost was actually true.
The function is interesting for both rd_device and rd_monitor so make
it part of the rd_device public API to avoid duplicated code.
The decision to move the function to reserve.c is motivated by the fact
that other projects (i.e. jack) use reserve.c only. Therefore, adding a
reserve->reserve-monitor dependency should be avoided.
