Fix coverage build error
Fix coverage build error

No need to run coverage on flaky tests suite, if it is empty

Change-Id: Ib63f52f84478d79221ee67d6e3f76ab976c71d3a
Partial-Bug: 1596630

tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller