use NULL to load plugins from default plugin directory

src/manager/Makefile.am

@@ -17,7 +17,6 @@ AM_CFLAGS = -rdynamic \
   -DSTRONGSWAN_CONF=\"${strongswan_conf}\" \
   -DIPSECDIR=\"${ipsecdir}\" \
   -DIPSEC_PIDDIR=\"${piddir}\" \
-  -DIPSEC_PLUGINDIR=\"${plugindir}\"\
   -DPLUGINS=\""${libstrongswan_plugins}\""
 
 # Don't forget to add templates to EXTRA_DIST !!! How to automate?

src/manager/main.c

@@ -35,7 +35,7 @@ int main (int arc, char *argv[])
 	int threads, timeout;
 
 	library_init(STRONGSWAN_CONF);
-	if (!lib->plugins->load(lib->plugins, IPSEC_PLUGINDIR,
+	if (!lib->plugins->load(lib->plugins, NULL,
 			lib->settings->get_str(lib->settings, "manager.load", PLUGINS)))
 	{
 		return 1;