Fix up 'net ads join' to delete and rejoin if the account already exists.

This fixes up a problem where a machine would join (or downgrade by trust
password change) to NT4 membership and not be able to regain full ADS
membership until a 'net ads leave'.

Andrew Bartlett

source/libsmb/cliconnect.c

@@ -1257,7 +1257,7 @@ again:
 	if (!cli_negprot(cli))
 	{
 		DEBUG(1,("failed negprot\n"));
-		nt_status = cli_nt_error(cli);
+		nt_status = NT_STATUS_UNSUCCESSFUL;
 		cli_shutdown(cli);
 		return nt_status;
 	}