alsa_sound:Port Audio fixes for concurrency and misc issues.

Issues:
 Support for echo supression .
   Fix:Add echo cancellation key to HAL getparameters

 Fix for IMS hold Issue. CRs-Fixed: 493474
   Fix:Add check for hold state also along with
       active to call doRouting.

 Increase the stop threshold of proxy driver for a2dp .
   Fix:Increase the stop threshold to a higher value so that stop is not
        issued while bt hal is not ready to consume data.

 If two back to back notifications are started immediately during a
 call, the second notification is still heard sometimes though it
 should be muted . CRs-Fixed: 501013
   Fix:Fix this issue by handling in call sonification even when refcount
       of output is 1, so that mute count is properly maintained in such
       scenarios

 Sound burst on switching from speaker to headset. CRs-Fixed: 480077
   Fix:Set the stream mute for other output(LPA or Compressed) followed
       by device setting for lpa or compressed output and then set the
       device for primary output

 Sudden burst for short duration. CRs-Fixed: 486123
   Fix:The delay calculation for unmute is not correct.
       Correct the calculation for unmute.

 Fix to avoid mute of an already muted stream. CRs-Fixed: 482262

 Fix to avoid Ringtone leaks to speaker in Skype MO call. CRs-Fixed: 477665

 When BT is in A2DP profile, try to do a Voice call,unable to
 hear any voice on BT/earpiece/Speaker when in call. enablevoicecall()
 is failed due to BTA2DP is not supported. CRs-Fixed: 462159
 Fix:Added check to detect voice path setup failures, such that
       later requests to setup voice path can be processed

 Observed that Skype call is not routing through HDMI sometimes.
   Fix: HDMI device pair gets overwritten by Earpiece & Mic when Skype
       closes current input stream and opens another one.
       Fix is to check the current rx device in audio HAL and picking up
       proper rx instead of handset_rx. CRs-Fixed: 478276

Change-Id: I242a0e37de6d3292ca564624f859ab3e5f16415d