Revert "devices: vhost-user: cras_snd: remove global executor variable"
Revert "devices: vhost-user: cras_snd: remove global executor variable"

This reverts commit 95d104fdd9136ef09a97cea10e04767a2deaa6f4.

Reason for revert: build fails with cras_snd enabled.

Original change's description:
> devices: vhost-user: cras_snd: remove global executor variable
>
> This variable can be passed as part of the backend structure.
>
> BUG=None
> TEST=cargo build
>
> Change-Id: Id8f905cc87de261a1a547da66fb93dafc1b7686d
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3451754
> Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
> Tested-by: kokoro <noreply+kokoro@google.com>
> Commit-Queue: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>

Bug: None
Change-Id: I4828944fadbbf1213533f737073de3a09befd740
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3474155
Tested-by: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>
Bot-Commit: Rubber Stamper <d516c4cc2192058ab8dae3d306acbdaf2ce6574f@appspot.gserviceaccount.com>
Reviewed-by: Woody Chow <cc0bff42e088f24a7e6e350b1e79cd0db9125d07@google.com>
Commit-Queue: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm