Cisco plugin fails with ParseError no elem found

When the Cisco nexus plugin is configured on DevStack, the tempest
Neutron API test test_port_list_filter_by_router_id fails with the
following error:
     ParseError: no element found: line 1, column 0

The root cause is that the Cisco Nexus plugin model layer
is encapsulating each dictionary response from the OVS subplugin
into a list, whereas the WSGI layer is expecting a dictionary
response. The fix is not to encapsulate these responses into a list.

Change-Id: I4b589e8e5696c0eae43cafc46912b3d7f29bbdb6
Closes-Bug: #1284162
return false or true according to binding result

Change-Id: I23a47c6c7c9be989e65c144b2277c42eeaaade3f
Closes-Bug: 1294500
Merge "Cisco plugin fails with ParseError no elem found"
Merge "return false or true according to binding result"