VTN Coordinator returns error in CSIT

When the CSIT Test cases are executed in sandbox, It is noted that the VTN Coordiantor returns 503 in some scenarios.

the current order of test cases is as follows

a. add controller
b. wait until the controller status is "up" to ensure that audit is complete

c. Continue to create vtn+vbridge+interface and portmaps to ensure some successful ping test using mininet.

The problem here is when the (c) executes, sometimes Coordinaotr returns 503 causing the tests to fail.

It needs to be analyzed what blocking operation occurs after the status is "up" as AUDIT is complete.