audio: do not invalidate stream used by voip

During the process of invalidation of voip streams,
actual driver is not closed so when it tries to open again
getoutput fails as only one instance of voip can be created.
so do not invalidate the tracks used by voip driver.
CRs-Fixed: 494093

Change-Id: I42a962991ce1d586d87f4aecba19c0e5dde6b9dd