Issue:When fetching dataflows for vlanmap in vbridge, and there is no interface present for the vbridge.

REPRODUCE SCENARIO:

Controller:

curl -v --user admin:adminpass -H 'content-type: application/json' -X POST -d '{"controller": {"controller_id": "controllerone", "ipaddr":"10.106.138.191", "type": "odc","version": "1.0", "auditstatus":"enable"}}' http://127.0.0.1:8083/vtn-webapi/controllers.json

VTN:

curl -v -X POST -H 'content-type: application/json' -H 'username: admin' -H 'password: adminpass' -d '{"vtn" : {"vtn_name":"vtn1","description":"test VTN" }}' http://127.0.0.1:8083/vtn-webapi/vtns.json

VBRIDGE:

curl -v -X POST -H 'content-type: application/json' -H 'username: admin' -H 'password: adminpass' -d '{"vbridge" : {"vbr_name":"vBridge2","controller_id":"controllerone","domain_id":"(DEFAULT)" }}' http://127.0.0.1:8083/vtn-webapi/vtns/vtn1/vbridges.json

VLANAMP:

curl -v -X POST -H 'content-type: application/json' -H 'username: admin' -H 'password: adminpass' -d '{"vlanmap" : {"vlan_id": 300 }}' http://127.0.0.1:8083/vtn-webapi/vtns/vtn1/vbridges/vBridge2/vlanmaps.json

DATAFLOWS:

curl -v -X GET -H 'content-type: application/json' --user 'admin:adminpass' -H 'ipaddr:127.0.0.1' "http://127.0.0.1:8083/vtn-webapi/dataflows?controller_id=controllerone&srcmacaddr=f64c.3e8c.49ef&vlan_id=300&switch_id=openflow:2&port_name=s2-eth2"

• About to connect() to 127.0.0.1 port 8083 (#0)
• Trying 127.0.0.1... connected
• Connected to 127.0.0.1 (127.0.0.1) port 8083 (#0)
• Server auth using Basic with user 'admin'
  > GET /vtn-webapi/dataflows?controller_id=controllerone&srcmacaddr=f64c.3e8c.49ef&vlan_id=300&switch_id=openflow:2&port_name=s2-eth2 HTTP/1.1
  > Authorization: Basic YWRtaW46YWRtaW5wYXNz
  > User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.15.3 zlib/1.2.3 libidn/1.18 libssh2/1.4.2
  > Host: 127.0.0.1:8083
  > Accept: /
  > content-type: application/json
  > ipaddr:127.0.0.1
  >
  < HTTP/1.1 500 Internal server error
  < Server: Apache-Coyote/1.1
  < Content-Type: application/json;charset=UTF-8
  < Content-Length: 554
  < Date: Fri, 12 Feb 2016 20:58:45 GMT
  <
• Connection #0 to host 127.0.0.1 left intact

OCCURANCE: Every time we fetch the dataflows for vlanmapping with no interface present in the configuration.