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

@@ -6,13 +6,4 @@ swanctl {
 
 charon-systemd {
   load = random nonce sha1 sha2 aes hmac pem pkcs1 x509 revocation constraints pubkey curve25519 gmp curl kernel-netlink socket-default resolve updown vici
-
-  syslog {
-    daemon {
-      default = 1
-    }
-    auth {
-      default = 0
-    }
-  }
 }

testing/tests/swanctl/dhcp-dynamic/hosts/dave/etc/strongswan.conf

@@ -6,13 +6,4 @@ swanctl {
 
 charon-systemd {
   load = random nonce sha1 sha2 aes hmac pem pkcs1 x509 revocation constraints pubkey curve25519 gmp curl kernel-netlink socket-default resolve updown vici
-
-   syslog {
-    daemon {
-      default = 1
-    }
-    auth {
-      default = 0
-    }
-  }
 }

testing/tests/swanctl/dhcp-dynamic/hosts/moon/etc/strongswan.conf

@@ -7,14 +7,6 @@ swanctl {
 charon-systemd {
   load = random nonce aes sha1 sha2 pem pkcs1 curve25519 gmp x509 curl revocation hmac vici kernel-netlink socket-default updown attr farp dhcp
 
-  syslog {
-    daemon {
-      default = 1
-    }
-    auth {
-      default = 0
-    }
-  }
   plugins {
     dhcp {
       server = 10.1.255.255