Fix flaky test TestServiceLegacy

User deferred barrier.signal() so panic definitely occurs before
we continue on in test.

Config reload uses recover() and increments config load counter, tests
were failing to see config load error counter increment.

Fixes: envoyproxy#256

Signed-off-by: Sunjay Bhatia <sunjayb@vmware.com>

test/service/ratelimit_legacy_test.go

@@ -121,7 +121,7 @@ func TestServiceLegacy(test *testing.T) {
 	t.configLoader.EXPECT().Load(
 		[]config.RateLimitConfigToLoad{{"config.basic_config", "fake_yaml"}}, gomock.Any()).Do(
 		func([]config.RateLimitConfigToLoad, stats.Scope) {
-			barrier.signal()
+			defer barrier.signal()
 			panic(config.RateLimitConfigError("load error"))
 		})
 	t.runtimeUpdateCallback <- 1