Use a 15s instead of 10s timeout on this test. The `default` subtest takes 9s on my laptop, so pad that for CI. (#11221)

command/agent_test.go

@@ -1415,7 +1415,7 @@ vault {
 				// the temp dir before Agent has had time to render and will
 				// likely fail the test
 				tick := time.Tick(1 * time.Second)
-				timeout := time.After(10 * time.Second)
+				timeout := time.After(15 * time.Second)
 				var err error
 				for {
 					select {