s3: Fix a bug in net's use of popt

In order to add --use-ccache to net, I added another "bool opt_ccache;" to
struct net_context. popt did not like this, it took a while to figure out why.
Popt has the lines

    /* XXX Check alignment, may fail on funky platforms. */
    if (arg == NULL || (((unsigned long)arg) & (sizeof(*arg)-1)))
        return POPT_ERROR_NULLARG;

The "bool opt_ccache;" was not aligned anymore...

source3/utils/net.h

@@ -70,7 +70,7 @@ struct net_context {
 	const char *opt_exclude;
 	const char *opt_destination;
 	int opt_testmode;
-	bool opt_kerberos;
+	int opt_kerberos;
 	int opt_force_full_repl;
 	int opt_single_obj_repl;
 	int opt_clean_old_entries;