Revert "[Testing, Hotword] Only check for hardware if the cras_audio_handler is initi...

Revert "[Testing, Hotword] Only check for hardware if the cras_audio_handler is initialized."

This reverts commit 7362cd971952961061648e657db7aae609c9e79f.
Reason for revert: This didn't fix the failure on valgrind test

>    [Testing, Hotword] Only check for hardware if the cras_audio_handler is init
>
>    Rather than creating a cras_audio_handler each time, only
>    check if the handler is initialized which avoids having to do
>    shutdown for tests that the hotword service is not relevant
>    to and should eliminate test interdependency.
>
>    Also, do init and shutdown in the hotword unittests since it
>    is relevant there.
>
>    BUG=442834
>    TBR=benwells@chromium.org, amistry@chromium.org
>
>    Review URL: https://codereview.chromium.org/814613002
>
>    Cr-Commit-Position: refs/heads/master@{#308902}

BUG=442834
TBR=rlp@chromium.org

Review URL: https://codereview.chromium.org/809373002

Cr-Commit-Position: refs/heads/master@{#308994}