disable rate limiter test

Summary:
The test is not stable because it relies on disk and only runs for a
short period of time. So misisng a compaction/flush would greatly affect
the rate. I am disabling it for now. What do you guys think?

Test Plan: make

Reviewers: yhchiang, igor, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19599

db/db_test.cc

@@ -7133,6 +7133,9 @@ TEST(DBTest, MTRandomTimeoutTest) {
 
 }  // anonymous namespace
 
+/*
+ * This test is not reliable enough as it heavily depends on disk behavior.
+ *
 TEST(DBTest, RateLimitingTest) {
   Options options = CurrentOptions();
   options.write_buffer_size = 1 << 20;         // 1MB
@@ -7201,6 +7204,7 @@ TEST(DBTest, RateLimitingTest) {
   fprintf(stderr, "write rate ratio = %.2lf, expected 0.5\n", ratio);
   ASSERT_TRUE(ratio > 0.4 && ratio < 0.6);
 }
+*/
 
 }  // namespace rocksdb