library/ipajoin.py: Drop unused subject base gathering from certificate

ipajoin is not called always and therefore we can no depend on the subject
base gathered from the certificate output of the join call.

library/ipajoin.py

@@ -129,7 +129,6 @@ from ipapython.version import NUM_VERSION, VERSION
 if NUM_VERSION < 40400:
     raise Exception, "freeipa version '%s' is too old" % VERSION
 from ipalib import errors
-from ipapython.dn import DN
 from ipaplatform.paths import paths
 try:
     from ipalib.install import sysrestore
@@ -336,13 +335,6 @@ def main():
         if already_joined and not os.path.exists(paths.KRB5_KEYTAB):
             module.fail_json(msg="krb5.keytab missing! Retry with ipaclient_force_join=yes to generate a new one.")
 
-        start = stderr.find('Certificate subject base is: ')
-        if start >= 0:
-            start = start + 29
-            subject_base = stderr[start:]
-            subject_base = subject_base.strip()
-            subject_base = DN(subject_base)
-
         if principal:
             run(["kdestroy"], raiseonerr=False, env=env)