[BUG] AudioPolicyManager: prevent unecessary force routing on SwOutput

At the begining/end of call, routing for all SwOutput is evaluated.
In case of using bridge, either the output involved in the SwBridge or
the output involved in the HwBridge for volume will be forced to be rerouted
on same device as the routing has already been evaluated for the Swoutput
hosting the call..

This CL implements this optimization.

Bug: 187173302

Test: CSV & VoIP calls

Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: I15102b661a4fc4afdd10888011feadf1fa7084ce