slapgrid: Remove .timestamp and .slapgrid always if partition is destroyed.

slapos/grid/slapgrid.py

@@ -1094,6 +1094,14 @@ stderr_logfile_backups=1
           software_url = None
         if computer_partition_state == COMPUTER_PARTITION_DESTROYED_STATE and \
            not software_url:
+          # Exclude files which may come from concurrent processing 
+          #  ie.: slapos ndoe report and slapos node instance commands 
+          # can create a .timestamp file.
+          file_list = os.listdir(computer_partition_path)
+          for garbage_file in [".slapgrid", ".timestamp"]:
+            if garbage_file in file_list:
+              shutil.rmtree(garbage_file)
+
           if os.listdir(computer_partition_path) != []:
             self.logger.warning("Free partition %s contains file(s) in %s." % (
                 computer_partition.getId(), computer_partition_path))