R1:bfe8f43f1a6f

Use "QUERY_STRING", not "REQUEST_URI", to parse raw request parameters

Summary:
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".

Test Plan: Visited `/oauth/google/?a=b`, got redirected with parameters preserved.

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