Fix error case memory bug in GetHostName() (#11544)

Summary:
Fix the error handling in `GetHostName` for non EFAULT, non EINVAL error. Current handling will cause stack overflow when non null-terminated c style string is in `name`, e.g. ENAMETOOLONG, when the `name` buffer is not big enough and the host name is truncated.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11544

Test Plan:
```
COMPILE_WITH_ASAN=1 make all check
```

Reviewed By: pdillinger

Differential Revision: D46775799

Pulled By: jowlyzhang

fbshipit-source-id: e0fc9400c50fe38bc1fd888b4fea5fe8706165bf

env/env_posix.cc

@@ -330,12 +330,16 @@ class PosixEnv : public CompositeEnv {
   }
 
   Status GetHostName(char* name, uint64_t len) override {
-    int ret = gethostname(name, static_cast<size_t>(len));
+    const size_t max_len = static_cast<size_t>(len);
+    int ret = gethostname(name, max_len);
     if (ret < 0) {
       if (errno == EFAULT || errno == EINVAL) {
         return Status::InvalidArgument(errnoStr(errno).c_str());
+      } else if (errno == ENAMETOOLONG) {
+        return IOError("GetHostName", std::string(name, strnlen(name, max_len)),
+                       errno);
       } else {
-        return IOError("GetHostName", name, errno);
+        return IOError("GetHostName", "", errno);
       }
     }
     return Status::OK();