rgw/sal: Add default shutdown method to filters

It simply calls `next->shutdown()`.

Fixes: https://tracker.ceph.com/issues/70771
Signed-off-by: Adam C. Emerson <[email protected]>

Author: adamemerson

src/rgw/rgw_sal_filter.h

@@ -488,6 +488,8 @@ class FilterDriver : public Driver {
   virtual const std::string& get_compression_type(const rgw_placement_rule& rule) override;
   virtual bool valid_placement(const rgw_placement_rule& rule) override;
 
+  virtual void shutdown(void) override { next->shutdown(); };
+
   virtual void finalize(void) override;
 
   virtual CephContext* ctx(void) override;