Fixes print error for keystone action with non-English characters

When processing keystone tenant-delete action with non-English
characters, printing the exception traceback will result in a
UnicodeEncodeError, so should encode text with safe_encode.

Fixes bug #1231472

Change-Id: Ic2599c51513189c132e31aa87d0d15df81802688
Merge "Fixes print error for keystone action with non-English characters"