fix(Router): replace state when normalized path is equal to current normalized path

Make sure the same path is not added multiple times to the history.
It is replacing the state, instead of skipping it completely,
because the current path in the browser might not be normalized,
while the given one is normalized.

Closes #7829

Closes #7897

modules/@angular/router-deprecated/test/integration/navigation_spec.ts

@@ -130,6 +130,22 @@ export function main() {
              });
        }));
 
+
+    it('should replace state when normalized paths are equal',
+       inject([AsyncTestCompleter, Location], (async, location) => {
+         compile(tcb)
+             .then((rtc) => {fixture = rtc})
+             .then((_) => location.setInitialPath("/test/"))
+             .then((_) => rtr.config([new Route({path: '/test', component: HelloCmp})]))
+             .then((_) => rtr.navigateByUrl('/test'))
+             .then((_) => {
+               fixture.detectChanges();
+               expect(fixture.debugElement.nativeElement).toHaveText('hello');
+               expect(location.urlChanges).toEqual(['replace: /test']);
+               async.done();
+             });
+       }));
+
     it('should reuse common parent components', inject([AsyncTestCompleter], (async) => {
          compile(tcb)
              .then((rtc) => {fixture = rtc})