Fixed crash in modifying Tunnel encryption endpoints
Fixed crash in modifying Tunnel encryption endpoints

1. TunnelTask has to be deleted only during TASK_EXIT.
   It was deleted in STOP_TASK as well which caused the
   crash.
2. If tunnel update happens for same entry, new tunnel
   task should not be created.

Change-Id: Ie6a4193def9c840ab095e1f3ae8eef01f3c09976
Closes-bug: #1779773

eonpatapon/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller