User tools have buggy group-authz dir loading

[labisso]

A file in the group-authz dir named group01.properties.orig breaks user tools ability to load the directory.

Traceback (most recent call last):
  File "/opt/nimbus/libexec//nimbus_list_users.py", line 122, in <module>
    rc = main()
  File "/opt/nimbus/libexec//nimbus_list_users.py", line 112, in main
    report_results(db, u, o)
  File "/opt/nimbus/libexec//nimbus_list_users.py", line 81, in report_results
    group = find_member(groupauthz_dir, o.dn)
  File "/opt/nimbus/web/src/python/nimbusweb/setup/groupauthz.py", line 57, in find_member
    for group in all_groups(groupauthz_dir):
  File "/opt/nimbus/web/src/python/nimbusweb/setup/groupauthz.py", line 31, in all_groups
    group_id = int(name[len(_GROUP_FILE_PREFIX):])
ValueError: invalid literal for int() with base 10: '01.properties'

[buzztroll]

Fixed. Added a test.