Only call pa_cvolme set on stream creation if volume explicitly set.

Streams without a custom volume set use suitable volume selected
by the PulseAudio server. This is usually the correct choice, since then
stream-restore module can apply old volume to the stream. Also with
Sailfish explicitly setting the volume to streams breaks system volume.

Change-Id: I75f5bf4e7aaafb4bd55510f5ac4ddf03767d494b
Done-with: Juho Hämäläinen <juho.hamalainen@tieto.com>
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>
Resource policy support for QSoundEffect.

Since sound effects are something short and mixed with other audio, do
not acquire resources explicitly. Follow the resources availability
information to determine when it is ok to play the sound effects.

When client has registered itself to resource manager, client's streams
are classified properly. If no higher priority client has acquired the
resources, isAvailable() is true, and sound effects can be played. We
do not explicitly acquire the resources, since then other clients with
the same resource class would lose the resources, thus not possible to
have second client play music with QMediaPlayer class while our client
would just want to play simple sound effects.

Change-Id: Ib5589349dca6900a8bee616b8ad77e7cb5ec9533
Done-with: Juho Hämäläinen <juho.hamalainen@tieto.com>
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>
Set volume only if volume was explicitly set.

Change-Id: I0d5abab0ffbf61a74c59ce240fd39e756479026b
Done-with: Juho Hämäläinen <juho.hamalainen@tieto.com>
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>