audioflinger: fix issue with camcorder and A2DP

Some audio HALs do not support well a device selection of 0 (no device)
received on an input stream.

This can happen because of a problem in the audioflinger code that handles
the forwarding of the output device selection to the record thread for use by
the pre processing modules that need it. If the output device is 0 (meaning
no op, which happens when stopping playback over A2DP) audioflinger could not
detect it was an output device selection and would forward it to the input
stream (see AudioFlinger::setParameters() and RecordThread::checkForNewParameters_l().

Issue 6179641.

Change-Id: Idae534521866538e0d12ba259a2834f402a922e2