deployed-server: start and enable network service

On the new versions of RHEL, the network service isn't enabled by
default because this mechanism became legacy.
However, our os-net-config doesn't use the new network manager, so we
still rely on on the network service to manage things like the virtual
bridges on the Undercloud and the Overcloud.

Closes-Bug: #1823353
Change-Id: I7094b36ef183dd388ea5a4c353f8eec43c9f2785

deployed-server/deployed-server-bootstrap-centos.sh

@@ -28,3 +28,7 @@ else
         ln -s -f /usr/bin/ansible-playbook /usr/local/bin/ansible-playbook-3
     fi
 fi
+
+# https://launchpad.net/bugs/1823353
+systemctl enable network
+systemctl start network

deployed-server/deployed-server-bootstrap-rhel.sh

@@ -25,3 +25,7 @@ else
         ln -s -f /usr/bin/ansible-playbook /usr/local/bin/ansible-playbook-3
     fi
 fi
+
+# https://launchpad.net/bugs/1823353
+systemctl enable network
+systemctl start network