TBR veyron/services/mounttable/lib: Fix test that I broke.

Change-Id: Ie0366f9c79da9f3b0005956d89cf4ccd6b187fef
diff --git a/services/mounttable/lib/mounttable_test.go b/services/mounttable/lib/mounttable_test.go
index 4919632..7de300b 100644
--- a/services/mounttable/lib/mounttable_test.go
+++ b/services/mounttable/lib/mounttable_test.go
@@ -661,8 +661,8 @@
 		boom(t, "Expected json parse error in acl file")
 	}
 	_, err = NewMountTableDispatcher("testdata/doesntexist.acl")
-	if err == nil {
-		boom(t, "Expected error from missing acl file")
+	if err != nil {
+		boom(t, "Missing acl file should not cause an error")
 	}
 }