Make sure the certificate cache is flushed when plugins are unloaded.

This avoids segmentation faults when plugins implementing cert_t are
already unloaded when the cache is flushed during destruction.

src/libcharon/daemon.c

@@ -115,6 +115,8 @@ static void destroy(private_daemon_t *this)
 	DESTROY_IF(this->public.connect_manager);
 	DESTROY_IF(this->public.mediation_manager);
 #endif /* ME */
+	/* make sure the cache is clear before unloading plugins */
+	lib->credmgr->flush_cache(lib->credmgr, CERT_ANY);
 	/* unload plugins to release threads */
 	lib->plugins->unload(lib->plugins);
 #ifdef CAPABILITIES_LIBCAP

src/libstrongswan/library.c

@@ -61,6 +61,9 @@ void library_deinit()
 	detailed = lib->settings->get_bool(lib->settings,
 								"libstrongswan.leak_detective.detailed", TRUE);
 
+	/* make sure the cache is clear before unloading plugins */
+	lib->credmgr->flush_cache(lib->credmgr, CERT_ANY);
+
 	this->public.scheduler->destroy(this->public.scheduler);
 	this->public.processor->destroy(this->public.processor);
 	this->public.plugins->destroy(this->public.plugins);

src/pluto/plutomain.c

@@ -852,6 +852,7 @@ void exit_pluto(int status)
 	delete_lock();
 	options->destroy(options);
 	pluto_deinit();
+	lib->credmgr->flush_cache(lib->credmgr, CERT_ANY);
 	lib->plugins->unload(lib->plugins);
 	libhydra_deinit();
 	library_deinit();