Revert "remove chroot when daemonizing (#640)"

This reverts commit 862a8a78b7.

bin/common/daemonize/unix.rs

@@ -8,7 +8,7 @@ use log::error;
 /// This function will redirect `stdout`, `stderr` to `/dev/null`,
 /// and follow the exact behavior in shadowsocks-libev
 pub fn daemonize<F: AsRef<Path>>(pid_path: Option<F>) {
-    let mut d = Daemonize::new().umask(0);
+    let mut d = Daemonize::new().umask(0).chroot("/");
     if let Some(p) = pid_path {
         d = d.pid_file(p);
     }