Move dnsmasq install into appropriate elements.

It was conflated with nova-compute, but it's really a networking
problem.

Change-Id: Ic67f48b55b079ae2ea845dcc19a0275522a9823a
Add missed file.

I missed this elements-deps when splitting out bm-dnsmasq.

Change-Id: I359085f2c3e06b6b2d33c9010148504a8cdfe467