python: wrap 'import dckeytab' in an explanatory function

The samba.dckeytab module has magic effects on samba.net, but never
appears to be used. That can be confusing, both to people and to
linters. Here we wrap that confusion up into a well-commented
function, so we never again have to wonder why the unused import is
there.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: David Mulder <dmulder@samba.org>

python/samba/tests/dckeytab.py

@@ -20,11 +20,15 @@ import os
 import sys
 import string
 from samba.net import Net
-import samba.dckeytab
+from samba import enable_net_export_keytab
+
 from samba import tests
 from samba.param import LoadParm
 
 
+enable_net_export_keytab()
+
+
 def open_bytes(filename):
     if sys.version_info[0] == 3:
         return open(filename, errors='ignore')