Changed nova-network install condition

openstack-network::server does not modify a node if
node['openstack']['compute']['network']['service_type'] is 'nova'.

Change check to use service_type attribute instead of server recipe so
that nova-network can be installed when using allinone-compute.

Change-Id: Iab969b30767d1d47fd5b55e805593a8d8548f0e9
Closes-Bug: #1267411
Merge "Changed nova-network install condition"