neutron::plugins::ml2::netwokring_ansible should be applied after
neutron::plugins::ml2, otherwise purge_config can remove the parameters
unexpectedly.
Also, all plugin packages should be install before configuration
completes, otherwise these packages can be missing when actual
code should be referred.
Change-Id: Ide4e65b6deac381df954341adbb804c9432d8643
90277442a1