TestNetworkShutdownCancelsIndefiniteRecoveryWait relied on an empty
upstream map never recovering. Since 73db7adc an empty pool checks
upstream.os instead, so the test probed the host's real OS resolver.
On a host with working DNS that check succeeds, recovery completes, and
it reads the upstream monitor the test never built.
Recover against a loopback port nothing listens on, so the wait can
never end on its own, and give the prog the upstream monitor that run
always creates before network monitoring can start a recovery. The
panic is test-only: production never reaches recovery without one.
Cuong Manh Le