util-lib: make sure fd_check_fstype() opens files with O_CLOEXEC

Also, O_NOCTTY is a safer bet, let's add that too.

src/basic/stat-util.c

@@ -204,7 +204,7 @@ int fd_check_fstype(int fd, statfs_f_type_t magic_value) {
 int path_check_fstype(const char *path, statfs_f_type_t magic_value) {
         _cleanup_close_ int fd = -1;
 
-        fd = open(path, O_RDONLY);
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY);
         if (fd < 0)
                 return -errno;