The rend_cache/entry_free was missing the rend cache allocation increment
before freeing the object.
Without it, it had an underflow bug:
Sep 17 08:40:13.845 [warn] rend_cache_decrement_allocation(): Bug: Underflow
in rend_cache_decrement_allocation (on Tor 0.4.5.0-alpha-dev
7eef9ced61)
Fixes#40125
Signed-off-by: David Goulet <dgoulet@torproject.org>