Clear sessions when session manager is done

It looks like there is no reason to keep sessions in the map beyond the
point where the session manager is considered done. This hopefully
simplifies the shutdown control flow a tiny bit.

src/fuzzers/fuzzer-setup.h

@@ -88,7 +88,7 @@ void fuzzer_cleanup_one_input() {
     zeek::event_mgr.Drain();
     zeek::session_mgr->Drain();
     zeek::event_mgr.Drain();
-    zeek::session_mgr->Clear();
+    zeek::session_mgr->Done();
     run_state::terminating = false;
 }
 

src/session/Manager.cc

@@ -82,12 +82,9 @@ Manager::Manager() {
     });
 }
 
-Manager::~Manager() {
+Manager::~Manager() { delete stats; }
-    Clear();
-    delete stats;
-}
 
-void Manager::Done() {}
+void Manager::Done() { Clear(); }
 
 Connection* Manager::FindConnection(Val* v) {
     zeek::detail::ConnKey conn_key(v);

src/zeek-setup.cc

@@ -391,7 +391,6 @@ static void terminate_zeek() {
 
     event_mgr.Drain();
 
-    session_mgr->Clear();
     plugin_mgr->FinishPlugins();
 
     finish_script_execution();