test_ipagetkeytab: fix missing import

The import was accidentally removed in commit
9a3d5fdadd.

https://fedorahosted.org/freeipa/ticket/5638

ipatests/test_cmdline/test_ipagetkeytab.py

@@ -33,6 +33,7 @@ from ipalib import errors
 from ipapython import ipautil, ipaldap
 from ipaserver.plugins.ldap2 import ldap2
 from ipapython.dn import DN
+from ipatests.test_cmdline.cmdline import cmdline_test
 
 def use_keytab(principal, keytab):
     try: