Points Newton to use openstack_hosts stable/newton

[antonym]

Changes newton branch to utilize openstack_hosts stable/newton branch instead of a sha to pull in https://github.com/rcbops/openstack-ansible-openstack_hosts/pull/4 and so we can avoid having to modify rpc-openstack in case we need to make future changes to openstack_hosts for newton.

The change mainly drops off the linux-extra-* from being installed due to the issues we were having with kernel version mismatches.

Mainly doing this so we can have this change in Newton and avoid having to change the Newton upgrade PR jobs that test this.

Fixes https://github.com/rcbops/rpc-upgrades/issues/368

[rpc-jenkins-svc]

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