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-dynamic/hosts/carol/etc/strongswan.conf

@@ -7,9 +7,6 @@ charon-systemd {
   integrity_test = yes
 
   syslog {
-    auth {
-      default = 0
-    }
     daemon {
       tnc = 3
       imc = 3

testing/tests/tnc/tnccs-dynamic/hosts/dave/etc/strongswan.conf

@@ -7,9 +7,6 @@ charon-systemd {
   integrity_test = yes
 
   syslog {
-    auth {
-      default = 0
-    }
     daemon {
       tnc = 3
       imc = 3

testing/tests/tnc/tnccs-dynamic/hosts/moon/etc/strongswan.conf

@@ -7,9 +7,6 @@ charon-systemd {
   integrity_test = yes
 
   syslog {
-    auth {
-      default = 0
-    }
     daemon {
       tnc = 3
       imv = 3