veyron/runtimes/google/ipc: Catch test error.

It seems that tests are occasionally failing in StartCall.
Catch that instead of having the test fail with a nil-dereference later
on.

Change-Id: Ic761ceba8663205e7f38022b47b12e29d729e6fe
diff --git a/runtimes/google/ipc/full_test.go b/runtimes/google/ipc/full_test.go
index 9e4f441..42f0a90 100644
--- a/runtimes/google/ipc/full_test.go
+++ b/runtimes/google/ipc/full_test.go
@@ -664,12 +664,14 @@
 	b.server.Publish("incompatible")
 
 	call, err := b.client.StartCall("incompatible/server/suffix", "Echo", []interface{}{"foo"})
-	expected := `method:"Echo",suffix:"suffix",arg:"foo"`
-	var result string
-	err = call.Finish(&result)
 	if err != nil {
+		t.Fatal(err)
+	}
+	var result string
+	if err = call.Finish(&result); err != nil {
 		t.Errorf("Unexpected error finishing call %v", err)
 	}
+	expected := `method:"Echo",suffix:"suffix",arg:"foo"`
 	if result != expected {
 		t.Errorf("Wrong result returned.  Got %s, wanted %s", result, expected)
 	}