Add extra encoding to ldap_dn verification

Relates #391.

Upstream `python-ldap` (surprisingly) does not support utf-8 DN. So
explicit encoding is needed.

Signed-off-by: Aaron Tan <jangsutsr@gmail.com>

awx/sso/tests/unit/test_ldap.py

@@ -15,7 +15,4 @@ def test_ldap_default_network_timeout(mocker):
     from_db = mocker.Mock(**{'order_by.return_value': []})
     with mocker.patch('awx.conf.models.Setting.objects.filter', return_value=from_db):
         settings = LDAPSettings()
-        assert settings.CONNECTION_OPTIONS == {
-            ldap.OPT_REFERRALS: 0,
-            ldap.OPT_NETWORK_TIMEOUT: 30
-        }
+        assert settings.CONNECTION_OPTIONS[ldap.OPT_NETWORK_TIMEOUT] == 30