crosvm: Fix --per-vm-core-scheduling option handling.
crosvm: Fix --per-vm-core-scheduling option handling.

Apparently the flag handling was forgotten to be
migrated in the switch to Argh crrev.com/c/3684144.

BUG=b:237216718
TEST=cheets_CTS_R.internal.arm.CtsVideo on Fizz.Kench

Change-Id: Ia967883cd5c4e2efcc1ca2cf97fd6adfc0bf163a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3746902
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Auto-Submit: Kazuhiro Inaba <9f510fc648c9b290f0723164b7d6bf691fb84794@chromium.org>

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