Description of problem:
The ipa group-remove-member command seems to require the user option althoug
that is not expected.


Version-Release number of selected component (if applicable):
ipa-server-3.0.0-37.el6.x86_64

How reproducible:
Every time


Steps to Reproduce:
1. Create test group
2. ipa group-add-member admins --groups test
3. ipa group-remove-member admins --groups test

Actual results:
[root@ipa SPECS]# ipa group-remove-member admins --groups test
ipa: ERROR: an internal error has occurred

Expected results:
Group membership should be removed

Additional info:
Adding a user option with a nonexisting user works around the issue:
[root@ipa SPECS]# ipa group-remove-member admins --groups test --users
nonexistinguser
  Group name: admins
  Description: Account administrators group
  GID: 200000000
  Member users: admin
  Failed members:
    member user: nonexistinguser: This entry is not a member
    member group:
---------------------------
Number of members removed 1
---------------------------