compute_ctl: Notify waiters when Postgres failed to start (#6034)

In case of configuring the empty compute, API handler is waiting on
condvar for compute state change. Yet, previously if Postgres failed to
start we were just setting compute status to `Failed` without notifying.
It causes a timeout on control plane side, although we can return a
proper error from compute earlier.

With this commit API handler should be properly notified.

compute_tools/src/bin/compute_ctl.rs

@@ -274,7 +274,13 @@ fn main() -> Result<()> {
             let mut state = compute.state.lock().unwrap();
             state.error = Some(format!("{:?}", err));
             state.status = ComputeStatus::Failed;
-            drop(state);
+            // Notify others that Postgres failed to start. In case of configuring the
+            // empty compute, it's likely that API handler is still waiting for compute
+            // state change. With this we will notify it that compute is in Failed state,
+            // so control plane will know about it earlier and record proper error instead
+            // of timeout.
+            compute.state_changed.notify_all();
+            drop(state); // unlock
             delay_exit = true;
             None
         }