set default attestation.service log level to crit

The service only normally logs to stderr with explicit priorities set
and anything other output indicates something is seriously wrong such as
a Java startup error.

systemd/system/attestation.service

@@ -27,6 +27,7 @@ RestrictAddressFamilies=AF_INET AF_INET6
 RestrictNamespaces=true
 RestrictRealtime=true
 RestrictSUIDSGID=true
+SyslogLevel=crit
 SystemCallArchitectures=native
 SystemCallFilter=@system-service
 SystemCallFilter=~@privileged @resources @obsolete