Fix query string processing in SPA SDK

The issue mostly affects Angular SDK but also takes place in the React SDK. When we are using URL rewriter without trailing slash redirect, the preview URL will be like `/site/_cmsinternal/spa-ssr?render_host=localhost`. In this case, the SDK sends Page Model API request to `http://localhost/site/_cmsinternal/spa-ssr/resourceapi/spa-ssr?render_host=localhost` which returns 404. The problem is, both of our SDKs incorrectly detect path because of the query string.

Way to reproduce:
1) Run the HAP with SSR SPA.
2) Go to http://localhost:3000/site/spa-ssr?something

Actual:
The browser shows 404.

Expected:
The browser shows the home page. The query string (`?something`) shouldn't give a difference.