In the multi process, the parent process instance Fdfs_client, the subprocess call will be destroy.

In Linux,In the multi process, the parent process instance Fdfs_client, the subprocess call will be destroy.

Because the code in `connection.py` 102:
```
if self.pid != os.getpid()
```

so,does this need to be changed into:
```
if self.pid != os.getpid() and self.pid != os.getppid():
```