config_lib: Switch vm_tests_supported -> vm_tests_override.

vm_tests_supported listed VM Tests to use if we needed to override the
VM Test list for heavier testing. vm_tests_override replaces it with a
(hopefully) more meaningful name, and changes the behavior so an
override value of None means use the original list unmodified.

This change implements this, and cleans up vm_test definitions in
chromeos_config a bit.

TEST=lint + run_tests + comparing --full config dumps from before/after.

Change-Id: I2557b84c87639e2645fb5c19d29eb4e5f0f4b700
Trybot-Ready: Don Garrett <>
Tested-by: Don Garrett <>
Reviewed-by: Prathmesh Prabhu <>
Commit-Queue: Don Garrett <>
4 files changed