Protected content appears before role validation is complete

### vue & vue-router-permissions version
Vue -- 2.5.21
Vue Router -- 3.0.2

### Reproduction Link
Out of the box

### Steps to reproduce
Setup access per documentation. Notice how when you have a protected route, it will flash before redirecting when access is not allowed.

### What is Expected?
Protected content will not be shown during access validation. Should most likely tie into VueRouter's navigation guards logic (ie `beforeEach`) to bring validation higher up the chain.

### What is actually happening?
Protected content is appearing on screen before access validation is performed and executed.