Added association support samples to network API

Modified: src/wadls/compute-api/src/ext/os-networks.wadl to link to samples in api_samples
- Disassociate only host from network
- Disassociate only project from network
- Associate network with host
Deleted:  src/wadls/compute-api/src/ext/samples/os-networks-disassociate.json (pointed to the xml/json in api_samples too).

Change-Id: Ia0960f396d6e07c0e2573594d150f40e742dd515
Fixes: bug 1077556