Update docker-plugin to 1.6 in config-internal.xml

This is already done in config-external.xml

Change-Id: I3be1aedcfe7cb4c02443a8cb4f9fba047ec2a6e8
diff --git a/jenkins-docker/server/config-internal.xml b/jenkins-docker/server/config-internal.xml
index 5e828fa..160f4f9 100644
--- a/jenkins-docker/server/config-internal.xml
+++ b/jenkins-docker/server/config-internal.xml
@@ -40,7 +40,7 @@
   <viewsTabBar class="hudson.views.DefaultViewsTabBar"/>
   <myViewsTabBar class="hudson.views.DefaultMyViewsTabBar"/>
   <clouds>
-    <com.nirima.jenkins.plugins.docker.DockerCloud plugin="docker-plugin@1.2.10">
+    <com.nirima.jenkins.plugins.docker.DockerCloud plugin="docker-plugin@1.6">
       <name>dockerhost</name>
       <templates>
         <com.nirima.jenkins.plugins.docker.DockerTemplate>