Determine menu base path from request base path and backend mount prefix instead of generating url.
Determine menu base path from request base path and backend mount prefix instead of generating url.

Fixes #6139 The base url generated could have query params or fragment which breaks urls that are concatenated to it.

romulo1984/bolt,HonzaMikula/masivnipostele,GawainLynch/bolt,electrolinux/bolt,nikgo/bolt,nikgo/bolt,romulo1984/bolt,HonzaMikula/masivnipostele,bolt/bolt,GawainLynch/bolt,bolt/bolt,nikgo/bolt,lenvanessen/bolt,lenvanessen/bolt,electrolinux/bolt,lenvanessen/bolt,bolt/bolt,HonzaMikula/masivnipostele,electrolinux/bolt,GawainLynch/bolt,romulo1984/bolt,lenvanessen/bolt,bolt/bolt,electrolinux/bolt,HonzaMikula/masivnipostele,GawainLynch/bolt,nikgo/bolt,romulo1984/bolt