swarm-controller: guard the agent-identity test that can reach the live store

`mint_agent_identity_node_runs_end_to_end_and_fails_without_the_agent_pki_named`
runs a `MintAgentIdentity` node, which calls `store::connect()` directly
rather than through `AppState`. It stops before that login only while
`SWARM_CONTROLLER_AGENT_PKI_MOUNT` and `SWARM_CONTROLLER_AGENT_PKI_ROLE`
are unset; with both set and `BAO_*` set it reaches a real store. The test
now refuses to run with them set. It still runs with `BAO_*` set, since
without the agent PKI it never gets as far as the login.

swarm-controller/src/main.rs

@@ -4091,6 +4091,16 @@ mod tests {
     /// variable, and creates the agent anyway.
     #[tokio::test]
     async fn mint_agent_identity_node_runs_end_to_end_and_fails_without_the_agent_pki_named() {
+        let pki = [
+            crate::agent_identity::ENV_AGENT_PKI_MOUNT,
+            crate::agent_identity::ENV_AGENT_PKI_ROLE,
+        ];
+        assert!(
+            pki.iter().all(|var| std::env::var_os(var).is_none()),
+            "{} and {} must be unset: with them set this test would reach a live store",
+            pki[0],
+            pki[1]
+        );
         let mut sched = hive_jobq::scheduler::Scheduler::new(
             hive_jobq::Graph::new(),
             hive_jobq::resources::ResourceTable::new(),