s4-tests/bind.py: Use samba.tests.connect_samdb() instead of directly using SamDB...

s4-tests/bind.py: Use samba.tests.connect_samdb() instead of directly using SamDB class

connect_samdb() functino will correctly handle things like:
- session_info param - it will create system_session() using supplied
  LoadParm parameter and thus avoiding creation of multiple LoadParm
  instances (LoadParm() will mask certain command line supplied options)
- host url will be prefixed with ldap:// automatically

Autobuild-User: Kamen Mazdrashki <kamenim@samba.org>
Autobuild-Date: Sun Nov 28 03:00:41 CET 2010 on sn-devel-104