be446abf45
the environment varible INSTANCE_ID is set when invoking boothooks from multi-part input. However, previously that was not the case for things run via bootcmd. This adds cloud-init-per, which makes it easy for user in bootcmd or boothook to do something per 'instance', 'always', or 'once'. The functionality in cloud-init-per mostly duplicated what was in cloud-init-run-module. That supported "modules", but it is unlikely that it was used for anything other than "execute". So, cloud-init-per now replaces cloud-init-run-module and provides legacy support for the 'execute' path.