Fix GCC 7 string truncation warning, too small temporary buffer

In GCC 7 the -Wall infers the new -Wformat-truncation which finds
problems with string truncation in functions like snprintf().

This patch fixes a possibly problem in path name creation which,
combined with the scandir() function, might cause loss of .conf
files, failure to call run-parts properly, and kill services at
shutdown.

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

src/exec.c

@@ -354,7 +354,7 @@ int run_parts(char *dir, char *cmd)
 		mode_t mode;
 		char *args[NUM_ARGS];
 		char *name = e[i]->d_name;
-		char path[CMD_SIZE];
+		char path[LINE_SIZE];
 
 		snprintf(path, sizeof(path), "%s/%s", dir, name);
 		mode = fmode(path);