gpo: Make the gpoupdate script much more reliable

gpo: Make the gpoupdate script much more reliable

Using a static file blanks the file when samba_gpoupdate crashes. Transformed
to a tdb file and added transactions. Add info logging to monitor gpo changes,
etc. Also handle parse errors and log an error message, then recover. Modified
the parsing code to use ConfigParser. Also, use the backslash in path names
when opening smb files, otherwise it fails against a windows server.

Signed-off-by: David Mulder <dmulder@suse.com>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>