Do not crash with "swift list --lh" for Ceph RadosGW.

If 'x-timestamp' header is not present in 'swift list' result,
date string cannot be correctly generated. Check for correct
exception to catch this case and return a special string value.
This is just a workaround for faulty RadosGW behavior.

Change-Id: I172843a2668e33efac00924906ff0dca3e790050
Closes-Bug: 1349528

swiftclient/shell.py

@@ -421,7 +421,7 @@ def st_list(parser, args, output_manager):
                                         float(meta.get('x-timestamp')))
                                     datestamp = strftime(
                                         '%Y-%m-%d %H:%M:%S', utc)
-                                except ClientException:
+                                except TypeError:
                                     datestamp = '????-??-?? ??:??:??'
                                 if not options.totals:
                                     output_manager.print_msg(