Move _clients to cmd dir

Make clients public and accepting parameters. Python functions
should be not connected to environ, cause that is there only for
CLI use. This lib will be called e.g. from UI.

Making clients public unifies creating clients in all places,
it should help with future version changes of the clients.

Move _clients to CMD dir, where it is defaulted to os.environ
values and call public clients with those default values.

Change-Id: Ic490d9cfb4069809c8b3142f62f3dd40644a0cf7