This plumbs through an "--use-nm" flag to glean which instructs it to
setup interface bringup with NetworkManager rather than legacy network
enablement scripts.
In this case, install the NetworkManager package. In the non-nm case,
also install the network-scripts for Fedora 29 -- this has stopped
being installed by default (it's been deprecated since forever).
As noted in the docs, this is currently really only relevant on the
supported rpm distros which are using the ifcfg-rh NetworkManager
plugin to effectively re-use old config files. However,
NetworkManager has similar plugins for other platforms, so support can
be expanded if changes are proposed.
Depends-On: https://review.openstack.org/618964
Change-Id: I4d76e88ce25e5675fd5ef48924acd09915a62a4b
