raw: Refactor RawServlet:getBranch and :getPath parameters

raw: Refactor RawServlet:getBranch and :getPath parameters

Refactor the `getBranch` and `getPath` methods to take a String as
second parameter, which is the already sanitised path info. Don't get
the path info from a passed in request anymore.

The methods are only ever called from within `processRequest`, which
already does some checks on the path info, like removing a leading
slash character. So no need to do that every time again the methods
and passing a request for that.