Using empty stateStartApiSuccess to indicate success

[longquanzheng]

iwf/service/interpreter/workflowImpl.go

Line 752 in 6d54278

commandRes.StateStartApiSucceeded = iwfidl.PtrBool(errStartApi == nil)

99.99% of the time, the value is true and we have to pass "stateStartApiSuccess":true to worker. We could make the field default as true so that we don't have to send this value.

However, a bool field default to true may be a bit confusing, so we could rename it to stateWaitUntilFailed in the IDL.
SDK can be adapted to the value