Disable EnvPosixTest::FilePermission

Summary:
The test is flaky in our CI but could not be reproduce manually on the same CI host. Disabling it.
Closes https://github.com/facebook/rocksdb/pull/3753

Differential Revision: D7716320

Pulled By: yiwu-arbug

fbshipit-source-id: 6bed3b05880c1d24e8dc86bc970e5181bc98fb45

env/env_test.cc

@@ -167,7 +167,7 @@ TEST_F(EnvPosixTest, AreFilesSame) {
 #endif
 
 #ifdef OS_LINUX
-TEST_F(EnvPosixTest, FilePermission) {
+TEST_F(EnvPosixTest, DISABLED_FilePermission) {
   // Only works for Linux environment
   if (env_ == Env::Default()) {
     EnvOptions soptions;