Remove unused imports

This patch removes unused imports, alse pylint has been configured to
check unused imports.

Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipatests/test_cmdline/test_ipagetkeytab.py

@@ -27,11 +27,9 @@ from ipalib import api
 from ipalib import errors
 import tempfile
 from ipapython import ipautil, ipaldap
-import nose
 import tempfile
 import gssapi
 from ipaserver.plugins.ldap2 import ldap2
-from ipapython.dn import DN
 import pytest
 
 def use_keytab(principal, keytab):