Error messages are displayed when the port updated with qos policy stating

Error messages are displayed when the port updated with qos policy stating
that binding are not allowed to the port

Following Error message was seen  when the same port updated with second
qos policy:

2017-04-05 14:42:54,116 | ERROR | pool-39-thread-7 |
FlowBasedServicesConfigListener  | 338 -
org.opendaylight.genius.interfacemanager-impl - 0.1.4.SNAPSHOT | Service
Binding entry update not allowed for:
b193e270-8053-4650-8059-a8ec57713069, Data:
BoundServices{getServiceName=qos.b193e270-8053-4650-8059-a8ec57713069,
getServicePriority=3, getServiceType=class
org.opendaylight.yang.gen.v1.urn.opendaylight.genius.interfacemanager.servicebinding.rev160406.ServiceTypeFlowBased,
augmentations={interface
org.opendaylight.yang.gen.v1.urn.opendaylight.genius.interfacemanager.servicebinding.rev160406.StypeOpenflow=StypeOpenflow{getFlowCookie=67108865,
getFlowPriority=10,
getInstruction=[Instruction{getInstruction=GoToTableCase{getGoToTable=GoToTable{getTableId=90,
augmentations={}}, augmentations={}}, getOrder=1, augmentations={}}]}}}

Use case:

- create a port, say port1
- create qos policy q1 with dscp and bandwidth
- Associate qos policy to the port
- observe the policy applied properly
- update the port again with qos policy q2
- Though the 2nd qos policy (here q2) seen applied properly , below error
  message was seen in ODL side:

  "Service Binding entry update not allowed"

  RCA:

  Qos service binding is happening even during the 2nd qos policy updation
  on the same port on which a 1st qos policy already associated.

Change-Id: Ia3754833d716f1e387bd7bdce00f82ed51a394ce
Signed-off-by: A Vamsikrishna <a.vamsikrishna@ericsson.com>