[Security] Keep other query string parameters when switching users

| Q                    | A
| ---------------------- | --- 
| Bug fix? 	        | yes
| New feature? 	| no
| BC breaks? 	| no
| Deprecations? 	| no
| Tests pass? 	| yes
| Fixed tickets 	| n/a
| Doc PR 	        | n/a

When switching users, the whole query string gets dropped when redirecting after the switch.
I think only the switch user parameter should be dropped from the query string.