clean old handlers before adding new one (#2400)

It's not a problem for production, but during tests there might be
multiple handlers added.

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>

Author: njzjz

deepmd/loggers/loggers.py

@@ -229,6 +229,8 @@ def set_log_handles(
 
     ch.setLevel(level)
     ch.addFilter(_AppFilter())
+    # clean old handlers before adding new one
+    root_log.handlers.clear()
     root_log.addHandler(ch)
 
     # * add file handler ***************************************************************