Fix race in get_network(s) in OVS plugin

Load network bindings eagerly with networks.
Otherwise a different db query could try to fetch network bindings
for already deleted networks. The issue is reproducible with
concurrent tempest network API tests.

Closes-Bug: 1263686
Change-Id: I0521ab162220c66a62491ff8e7e4a9f6d7bef6c4
Rename nicira configuration elements to match new naming structure

- Every config item prefixed with nvp is prefixed with nsx
- deprecation qualifiers are added to preserve bw compatibility
- nicira/nvp.ini is renamed to vmware/nsx.ini
- symlink nicira/nvp.ini is created to point to vmware/nsx.ini
- UT added to verify that nvp.ini and old config items can still
  parsed correctly; bw-compat will be dropped in Juno

Partial-implements blueprint nicira-plugin-renaming

Change-Id: I676b868e61064cc5ff17e2246e83ba5c5e4a3449
Merge "Fix race in get_network(s) in OVS plugin"
Merge "Rename nicira configuration elements to match new naming structure"