fs-util: rename path_is_safe() → path_is_normalized()

Already, path_is_safe() refused paths container the "." dir. Doing that
isn't strictly necessary to be "safe" by most definitions of the word.
But it is necessary in order to consider a path "normalized". Hence,
"path_is_safe()" is slightly misleading a name, but
"path_is_normalize()" is more descriptive, hence let's rename things
accordingly.

No functional changes.

src/basic/fs-util.c

@@ -509,7 +509,7 @@ static int getenv_tmp_dir(const char **ret_path) {
                         r = -ENOTDIR;
                         goto next;
                 }
-                if (!path_is_safe(e)) {
+                if (!path_is_normalized(e)) {
                         r = -EPERM;
                         goto next;
                 }
@@ -707,7 +707,7 @@ int chase_symlinks(const char *path, const char *original_root, unsigned flags,
 
                         if (errno == ENOENT &&
                             (flags & CHASE_NONEXISTENT) &&
-                            (isempty(todo) || path_is_safe(todo))) {
+                            (isempty(todo) || path_is_normalized(todo))) {
 
                                 /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
                                  * what we got so far. But don't allow this if the remaining path contains "../ or "./"