BZ #1104093 -  Foreman default config is NOT ML2.

https://bugzilla.redhat.com/show_bug.cgi?id=1104093

Makes ML2 the default core plugin for neutron in Quickstack.
Merge pull request #249 from jguiditta/icehouse_ml2

BZ #1104093 -  Foreman default config is NOT ML2.