Fixes T13260. "QUERY_STRING" and "REQUEST_URI" are similar for our purposes here, but our nginx documentation tells you to pass "QUERY_STRING" and doesn't tell you to pass "REQUEST_URI". We also use "QUERY_STRING" in a couple of other places already, and already have a setup check for it.

Use "QUERY_STRING" instead of "REQUEST_URI".

Visited /oauth/google/?a=b, got redirected with parameters preserved.