Make os-net-config depend on openvswitch

This makes sense because pretty much all our low level
networking models make use of openvswitch. Also,
you need Openvswitch to be installed (and running)
before any of the os-refresh-config hooks for
os-net-config will work.

Change-Id: Ieff88a48a1e28fa32c343ae1eeea9fec4aa3df26
Merge "Make os-net-config depend on openvswitch"