use region quarantine even if MAP_FIXED call fails

This is a more sensible way of handling an out-of-memory failure in this
edge case. It doesn't matter much in practice.

h_malloc.c

@@ -839,10 +839,10 @@ static void regions_quarantine_deallocate_pages(void *p, size_t size, size_t gua
     }
 
     if (unlikely(memory_map_fixed(p, size))) {
-        deallocate_pages(p, size, guard_size);
-        return;
+        memory_purge(p, size);
+    } else {
+        memory_set_name(p, size, "malloc large quarantine");
     }
-    memory_set_name(p, size, "malloc large quarantine");
 
     struct quarantine_info target =
         (struct quarantine_info){(char *)p - guard_size, size + guard_size * 2};