cmdline: Refactor cfg.protected_vm initialization
cmdline: Refactor cfg.protected_vm initialization

De-duplicate logic for when the VM isn't protected.

Note: no functional change intended.

BUG=b:243646855
TEST=build

Change-Id: I27dd23e8c437e4e0adb7d344cc3a8b86557672e8
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3867613
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: Pierre-Clément Tosi <2823ff726385ec3ac1cbf6edb75016ef1c0f9dc0@google.com>

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