audiopolicy: avoid unnecessary closure of HOTWORD recording.

When the new selected input device is not supported by current
input handle, normally it needs to be closed and then create
a new one to capture with the new device.
While for HOTWORD recording, as the data will either be captured
from handset mic or headset mic, recording can be continued on
the original input handle.

Bug: 179399190
Test: audio smoke tests
Change-Id: I01ad15fa2bb383979250399fe2b8903965bb6aa9