Add unit test case

Signed-off-by: Matt Lord <mattalord@gmail.com>

go/vt/vtctl/workflow/server.go

@@ -1985,9 +1985,6 @@ func (s *Server) dropTargets(ctx context.Context, ts *trafficSwitcher, keepData,
 					return nil, err
 				}
 			}
-			if err := sw.dropSourceDeniedTables(ctx); err != nil {
-				return nil, err
-			}
 			if err := sw.dropTargetDeniedTables(ctx); err != nil {
 				return nil, err
 			}

go/vt/vtctl/workflow/server_test.go

@@ -372,6 +372,33 @@ func TestMoveTablesComplete(t *testing.T) {
 					workflowName, targetKeyspaceName),
 			},
 		},
+		{
+			name: "ignore source keyspace",
+			sourceKeyspace: &testKeyspace{
+				KeyspaceName: sourceKeyspaceName,
+				ShardNames:   []string{"0"},
+			},
+			targetKeyspace: &testKeyspace{
+				KeyspaceName: targetKeyspaceName,
+				ShardNames:   []string{"-80", "80-"},
+			},
+			req: &vtctldatapb.MoveTablesCompleteRequest{
+				TargetKeyspace:       targetKeyspaceName,
+				Workflow:             workflowName,
+				IgnoreSourceKeyspace: true,
+			},
+			expectedTargetQueries: []*queryResult{
+				{
+					query: fmt.Sprintf("delete from _vt.vreplication where db_name = 'vt_%s' and workflow = '%s'",
+						targetKeyspaceName, workflowName),
+					result: &querypb.QueryResult{},
+				},
+			},
+			want: &vtctldatapb.MoveTablesCompleteResponse{
+				Summary: fmt.Sprintf("Successfully completed the %s workflow in the %s keyspace",
+					workflowName, targetKeyspaceName),
+			},
+		},
 		{
 			name: "named lock held",
 			sourceKeyspace: &testKeyspace{