[VOL-1644]  Add test cases to the Core Utils package

As part of this update some utilities which were inside the flow
decomposer file has been moved to the utils package.  Otherwise,
the code would have to be duplicated to work around package
circular dependencies.

Change-Id: I77dc6cdb23d832323e58ff6d9351db809fff30ba
diff --git a/rw_core/utils/core_utils.go b/rw_core/utils/core_utils.go
index cf77d59..813c978 100644
--- a/rw_core/utils/core_utils.go
+++ b/rw_core/utils/core_utils.go
@@ -59,12 +59,12 @@
 		if !ok { // closed channel
 			//Set the channel at that index to nil to disable this case, hence preventing it from interfering with other cases.
 			cases[index].Chan = reflect.ValueOf(nil)
-			errors[index] = status.Errorf(codes.Internal, "channel closed")
+			errors[index] = status.Error(codes.Internal, "channel closed")
 			errorsReceived = true
 		} else if index == len(chnls) { // Timeout has occurred
 			for k := range errors {
 				if !resultsReceived[k] {
-					errors[k] = status.Errorf(codes.Aborted, "timeout")
+					errors[k] = status.Error(codes.Aborted, "timeout")
 				}
 			}
 			errorsReceived = true