[config] Change private validate functions to arity 2

Some configuration validation must be within the context of a validated
machine, but the individual validate methods did not have access to that
data. This commit makes all of the individual validate methods arity 2,
for the error array and the currently validating machine.
[config/global] Allow PE versions to include rc builds
[config/pe_bootstrap] Don't revalidate version

The parent method definition of Config::PEBootstrap#validate already
calls #validate_version, we shouldn't call it again in the child class.
[provisioner/pe_boostrap] Finalize global config first
Merge branch 'config-validate-arity'