Only get dexpreopt config for device modules

Calling dexpreopt.GetGlobalConfig can return errors, move the checks
that don't depend on dexpreopt.GetGlobalConfig first to avoid
breaking all modules when the global config is invalid, for example
in a partial branch that is missing the BootProfileImages file.

Bug: 207813628
Test: tradefed branch builds
Change-Id: Id1689de3f1ef986a41a60622cb357edb9d323b8a