daemon: initialize mask_orig with sigemptyset()

consolidation of variable declarations and initializations in previous
commit allowed me to detect that one of the signal masks is not properly
initialized with sigemptyset (as man 3 sigsetops demands)

Reviewed by:	kevans
Pull Request:	https://github.com/freebsd/freebsd-src/pull/669

usr.sbin/daemon/daemon.c

@@ -171,6 +171,7 @@ main(int argc, char *argv[])
 	sigemptyset(&mask_susp);
 	sigemptyset(&mask_read);
 	sigemptyset(&mask_term);
+	sigemptyset(&mask_orig);
 
 	while ((ch = getopt_long(argc, argv, shortopts, longopts, NULL)) != -1) {
 		switch (ch) {