test(forms): added missing selfOnly tests (#12317)

modules/@angular/forms/test/form_control_spec.ts

@@ -429,6 +429,12 @@ export function main() {
         expect(c.value).toBe('initial value');
       });
 
+      it('should not set the parent when explicitly specified', () => {
+        const g = new FormGroup({'one': c});
+        c.patchValue('newValue', {onlySelf: true});
+        expect(g.value).toEqual({'one': 'initial value'});
+      });
+
       it('should reset to a specific value if passed with boxed value', () => {
         c.setValue('new value');
         expect(c.value).toBe('new value');