Use the discovery client from api-venv instead of system discoveryclient
* VGW routes to be exported with encap type MplsoGre only
* Check for the same in test case
* WHile exporting route, check if the particular encap type is set
  before exporting
Fixed an issue with the extraction of table name in delrequest.lua, because of which the UVE keys are not removed from the table in redis-uve.