passdb: Use common code in cli_credentials_set_machine_account_db_ctx()

passdb: Use common code in cli_credentials_set_machine_account_db_ctx()

This avoids some duplication in setting the machine account passsword
for the domain member and DC case.

This does not yet remove the duplication, that requires a bigger
restructure of the various routines used here to obtain the machine
and domain trust secrets.

Also no longer used is the timeout/2 code to not set the previous
password.  It is now always passed to the caller.

Andrew Bartlett

Change-Id: Idd5bafedf4cbac30b174955d743ec4128a6902ee
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>