DO NOT MERGE: Revert "Remove StuckServer using backlog and tests relying on it"

This reverts commit 8ffb0f55.
(DO NOT MERGE because the original CL was a cherry-pick form N,
where this wasn't a problem. It breaks trees only on M.)

It didn't block 'm cts' but it broke other targets.
libcore/luni/src/test/java/libcore/java/net/URLConnectionTest.java
still had a reference to StuckServer.


Change-Id: If9486b5b552c4992536507da5460436fb8185df3