Fix python3 compatibility on LDAP search DN from id
Fix python3 compatibility on LDAP search DN from id

In Python 3, python-ldap no longer allows bytes for some fields (DNs,
RDNs, attribute names, queries). Instead, text values are represented
as str, the Unicode text type.

[1] More details about byte/str usage in python-ldap can be found at:
http://www.python-ldap.org/en/latest/bytes_mode.html#bytes-mode

Change-Id: I63e3715032cd8edb11fbff7651f5ba1af506dc9d
Related-Bug: #1798184

openstack/keystone,openstack/keystone,mahak/keystone,mahak/keystone,mahak/keystone,openstack/keystone