Fixes regarding memory management

Fixes assorted issues identified by valgrind.

src/modsecurity.cc

@@ -66,6 +66,10 @@ ModSecurity::~ModSecurity() {
 #ifdef WITH_GEOIP
     Utils::GeoLookup::getInstance().cleanUp();
 #endif
+    delete m_global_collection;
+    delete m_ip_collection;
+    delete m_session_collection;
+    delete m_user_collection;
 }