audio policy: fix concurrent capture policy for virtual sources

Do not consider virtual sources when determining
lastest active capture client. As a virtual source
capturing does not silence other captures, it should not
prevent another client from being selected as the latest active.

Bug: 160820363
Bug: 161725794
Test: Verify capture with Solotester in background and projecting to
DHU.

Change-Id: I2f28026dbecfa72b5d44f52b95538fc13996627b
Merged-In: I2f28026dbecfa72b5d44f52b95538fc13996627b
(cherry picked from commit 14a88630162b96d0d52354261ee09216c0bed0d7)
1 file changed