OpenSL ES: Be less rigid about tearing down the output device.

OpenSL ES: Be less rigid about tearing down the output device.

We where very strict about tearing down the audio device. While this is
a good strategy to avoid unnecessary resource usage, it also causes
excessive re-allocations, e.g., when transiting from start to stop and
back again. This can increase latency, especially in case where a short
clip is re-played at a high frequency.
This change also decrease the chance of the player ending up in some
unknown state where it drops audio clips without any warning.

Task-number: QTBUG-40864
Change-Id: I1afad4af0622983f0f0c221d91cf794585d8cad2
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>