testing: Globally define logging via syslog for charon-systemd

We could make the same change for charon (actually setting it for charon
in strongswan.conf.testing would work for charon-systemd too), however,
there are dozens of test cases that currently set charondebug in
ipsec.conf.

testing/tests/tnc/tnccs-20-ev-pt-tls/hosts/alice/etc/strongswan.conf

@@ -4,12 +4,9 @@ charon-systemd {
   load = random nonce pem pkcs1 x509 openssl revocation constraints curl vici socket-default kernel-netlink tnc-pdp tnc-imv tnc-tnccs tnccs-20 sqlite
 
   syslog {
-    auth {
-      default = 0
-    }
     daemon {
       tls = 2
-      tnc = 2 
+      tnc = 2
       imv = 3
     }
   }
@@ -32,7 +29,7 @@ libtls {
 
 libimcv {
   database = sqlite:///etc/db.d/config.db
-  policy_script = /usr/local/libexec/ipsec/imv_policy_manager 
+  policy_script = /usr/local/libexec/ipsec/imv_policy_manager
 
   plugins {
     imv-swima {