service_register(): guard against loss of command args

We use strtok() quite extensively in .conf parser.  Parsing of a service
line is split in two, with the command arguments being parsed very late.

Adding a new sub-option parser, based on strtok(), risk losing command
arguments.  Thus, change to use strtok_r() so that we always know where
the arg parser is.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/tty.h

@@ -48,7 +48,7 @@ char	*tty_canonicalize (char *dev);
 int	 tty_isatcon      (char *dev);
 char	*tty_atcon	  (void);
 
-int	 tty_parse_args   (char *cmdline, struct tty *tty);
+int	 tty_parse_args   (struct tty *tty, char *cmd, char **args);
 
 int	 tty_exists	  (char *dev);
 int	 tty_exec	  (svc_t *tty);