Add posibility to configure logfile param

Change-Id: Iac37132f89dab9b489b864070022c5ddc926d006
diff --git a/tests/pillar/client.sls b/tests/pillar/client.sls
index 58ae2aa..fd770b7 100644
--- a/tests/pillar/client.sls
+++ b/tests/pillar/client.sls
@@ -1,6 +1,7 @@
 ntp:
   client:
     enabled: true
+    logfile: '/var/log/ntp.log'
     strata:
     - ntp.cesnet.cz
     - pool.ntp.org