Fix potential leak of audio input handle.

The audio input handle is ultimately owned by the audio recorder
object but it could be dropped on the floor if an error occurred
before that object was fully initialized.

Rearranged some of the argument validation and merged getInput_l
with openRecord_l to simplify the code and prevent such a leak
from occurring.

Bug: 10265163
Change-Id: I124dce344b1d11c2dd66ca5e2c9aec0c52c230e2