Implement multiple-clients integration test

Two transport connections to gateway sun are set up, one from client
carol and the other from client dave. The gateway sun uses the Trusted
Key Manager (TKM) and is the responder for both connections. The
authentication is based on X.509 certificates. In order to test the
connections, both carol and dave ping gateway sun.

testing/tests/tkm/multiple-clients/posttest.dat

@@ -0,0 +1,5 @@
+sun::DAEMON_NAME=charon-tkm ipsec stop
+sun::killall tkm_keymanager
+sun::rm -f /tmp/tkm.rpc.ike /tmp/tkm.rpc.ees /tmp/tkm.log
+carol::ipsec stop
+dave::ipsec stop