testing: Add tkm xfrmproxy-expire test

This test asserts that the handling of XFRM expire messages from the
kernel are handled correctly by the xfrm-proxy and the Esa Event Service
(EES) in charon-tkm.

testing/tests/tkm/xfrmproxy-expire/hosts/moon/etc/strongswan.conf

@@ -0,0 +1,8 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon-tkm {
+  dh_mapping {
+    15 = 1
+    16 = 2
+  }
+}