[FIX] http: nodb fallback in case of connection error

When calling a `auth=none` route with a non-existing DB name, the server
redirects to `/web/database/selector`. Such a route can be called
without database, therefore it is expected to work if the database
doesn't exist as well.

Before the HTTP refactoring, the fallback was `_dispatch_nodb` [1]. We
roll back to the same behavior since there is no good reason to redirect
to `/web/database/selector`.

Commits 4b330f3173 and de4e67dcc529163 are reintroduced as well.

[1] https://github.com/odoo/odoo/blob/b3199e949ae70307e8181ba0d6237871d6d07af7/odoo/http.py#L1529

closes odoo/odoo#104174

X-original-commit: 1565e85890f1d14e067edd1c198c7199ab536307
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>
Signed-off-by: Olivier Dony <odo@odoo.com>

odoo/http.py

@@ -1525,7 +1525,11 @@ class Request:
             self.db = None
             self.session.db = None
             root.session_store.save(self.session)
-            return self.redirect('/web/database/selector')
+            if request.httprequest.path == '/web':
+                # Internal Server Error
+                raise
+            else:
+                return self._serve_nodb()
 
         with contextlib.closing(self.registry.cursor()) as cr:
             self.env = odoo.api.Environment(cr, self.session.uid, self.session.context)