testing: Add CA ID mappings to TKM tests

Extend the build-certs-chroot script is to fill in the public key
fingerprint of the CA certificate in the appropriate strongswan.con
files.

testing/tests/tkm/host2host-xfrmproxy/hosts/moon/etc/strongswan.conf.in

@@ -0,0 +1,14 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon-tkm {
+  dh_mapping {
+    15 = 1
+    16 = 2
+  }
+  ca_mapping {
+    strongswan_ca {
+      id = 1
+      fingerprint = CA_SPK_HEX
+    }
+  }
+}