Increase wait time within EnvPosixTestWithParam.RunMany (#9413)

Summary:
We see:

[ RUN      ] ChrootEnvWithDirectIO/EnvPosixTestWithParam.RunMany/0
env/env_test.cc:464: Failure
Expected equality of these values:
  4
  cur
    Which is: 0

The suspicious is that the wait time is not long enough. Increase the wait time to 10s and allows earlier check.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9413

Test Plan: Run the test

Reviewed By: riversand963

Differential Revision: D33697715

fbshipit-source-id: 3d71715562a8cceb694b773276dd9e4e451a18bc

env/env_test.cc

@@ -459,10 +459,8 @@ TEST_P(EnvPosixTestWithParam, RunMany) {
   env_->Schedule(&CB::Run, &cb3);
   env_->Schedule(&CB::Run, &cb4);
 
-  Env::Default()->SleepForMicroseconds(kDelayMicros);
-  int cur = last_id.load(std::memory_order_acquire);
-  ASSERT_EQ(4, cur);
   WaitThreadPoolsEmpty();
+  ASSERT_EQ(4, last_id.load(std::memory_order_acquire));
 }
 #endif