Allow vendors to provide cloud-config via DynamicJSON vendor data

Current implementation of DynamicJSON wraps all responses to service-name specific objects. This behavior make cloud-init ignore vendor-specific cloud-config that could be used for hostname, updating packages or installing new one and not using user-data for this. This feature is supported by cloud-init https://cloudinit.readthedocs.io/en/latest/reference/datasources/openstack.html#vendor-data but not possible to use with current DynamicJSON vendor data implementation. Have to be implemented for open source project to allow vendors store cloud-config in Consul Key-Value in easy way https://github.com/ib-systems/openstack-consul-dynamic-vendordata