rm-rf: Make sure we rewinddir() before readdir()

We don't know what state the passed in file descriptor is in. Let's
make sure we rewind it before iterating over it.

Fixes #29606

src/shared/rm-rf.c

@@ -365,6 +365,10 @@ static int rm_rf_children_impl(
                                                                strna(path));
                                 }
                         }
+
+                        /* Make sure we reset the iterator since we don't know the state the passed in file
+                         * descriptor is in. */
+                        rewinddir(d);
                 }
 
                 FOREACH_DIRENT_ALL(de, d, return -errno) {