Close writers before switching modes

Author: vandanavk

smdebug/core/hook.py

@@ -457,6 +457,10 @@ def _write_state(self):
             self.state_store.update_state(current_state)
 
     def set_mode(self, mode):
+        # flush out any writes before switching modes
+        if self.writer is not None:
+            self._close_writers()
+
         # train
         if mode in ALLOWED_MODES:
             self.mode = mode