Return a NetworkInfo object instead of a list

This return a NetworkInfo object instead of a list when there are no
configured networks available.

Fixes bug #1222781

Change-Id: I59c88944253ed5ff8b567d79046c3065fdfed9ab
Fix HTTP response for PortNotFound during boot (v3 API)

If a non-existent Neutron port is passed as a network parameter during create
instance, Nova API should return a 404 error. This was fixed for the V2
API in commit 4721408ea861a66af1ad1df5a45c42addcd8a95f (though with a 400).
This applies the corresponding fix to the V3 API.

Fixes bug 1212137

Change-Id: I27dfba636635eb8ac257785b833b240bc439f9ff
Update allowvssprovider in xenstore_data

My previous commit was missing the vm-data part so the original
bug was still present.

The command line fix:
xe vm-param-set uuid={UUID} xenstore-data:vm-data/allowvssprovider=false

This commit adds vm-data to the xenstore message and will properly
disallow vss.

Fixes: bug #1112673

Change-Id: I85ef25a9b61795c98c12549f77cd7ca7305861d2
Merge "Update allowvssprovider in xenstore_data"
Merge "Return a NetworkInfo object instead of a list"
Merge "Fix HTTP response for PortNotFound during boot (v3 API)"