audio policy: fix getDeviceForStrategy()

Modification of getDEviceForStrategy by commit 28d09f064 made
wrong use of available output devices vector passed by reference
and caused an update of the actual list of connected devices instead
of the local list.

Bug: 27586202

Change-Id: I805b9cf27e1fb28494e6e23b2b874e0e5c3487e6
2 files changed