node-tools: only a call pattern names a caller, and a fall-back for want of a responder is said (hq issue 365, review)

callerOn reads a caller only under the call kind, so a tool subscription ending
in a wildcard never yields one. A caller-named call that reached nobody is said
once per subject before it is asked on the old subject, so a runtime or grant
that drifted behind is seen rather than a quiet unproven. The caller tests wait
for their bundle's exit, which reads the launcher's restart pauses another test
sets.

node-tools/internal/runtime/caller_test.go

@@ -27,7 +27,7 @@ func TestACallOnTheCallerNamedSubjectReachesTheModuleWithItsCaller(t *testing.T)
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer stop()
+	defer settled(stop)
 	asker, err := bus.Connect(bus.Credential{URL: mt.URL(t), Module: "node-tools", Node: "shanks",
 		User: "shanks.node-tools", Password: "unused"})
 	if err != nil {
@@ -65,7 +65,7 @@ func TestTheSubjectThatNamesNoCallerStillWorksAndNamesNone(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer stop()
+	defer settled(stop)
 	old, err := nats.Connect(mt.URL(t))
 	if err != nil {
 		t.Fatal(err)
@@ -89,3 +89,11 @@ func TestTheSubjectThatNamesNoCallerStillWorksAndNamesNone(t *testing.T) {
 		}
 	}
 }
+
+// settled stops a runtime and waits for its bundle's exit to be handled: the launcher reads its restart pauses
+// (launch.RestartFirst) as a bundle exits, and a later test in this package sets them, so a test that leaves its
+// bundle exiting behind it races the next one.
+func settled(stop func()) {
+	stop()
+	time.Sleep(500 * time.Millisecond)
+}