ksud: fix bind mount failed again (#395)

This fixes https://github.com/Dr-TSNG/ZygiskOnKernelSU/issues/18

userspace/ksud/src/event.rs

@@ -164,11 +164,13 @@ pub fn on_post_data_fs() -> Result<()> {
         warn!("load system.prop failed: {}", e);
     }
 
-    // mount moduke systemlessly by overlay
+    // mount module systemlessly by overlay
     if let Err(e) = mount_systemlessly(module_dir) {
         warn!("do systemless mount failed: {}", e);
     }
 
+    std::env::set_current_dir("/").with_context(|| "failed to chdir to /")?;
+
     Ok(())
 }