Don't compile ovs support when the RPM is built --without=ovs, to fix
the following error:

error: Installed (but unpackaged) file(s) found:
   /usr/lib/systemd/system/NetworkManager.service.d/NetworkManager-ovs.conf
   /usr/lib64/NetworkManager/libnm-device-plugin-ovs.so
   /usr/share/man/man7/nm-openvswitch.7.gz

Fixes: 830a5a14