Added extensible choice plugin, disable system reclass autotesting

Change-Id: I2f81741813de7df80903a7e081e6d65236a522a0
diff --git a/jenkins/client/init.yml b/jenkins/client/init.yml
index 191527f..ab057df 100644
--- a/jenkins/client/init.yml
+++ b/jenkins/client/init.yml
@@ -25,6 +25,7 @@
         discard-old-build: {}
         docker-workflow: {}
         extended-choice-parameter: {}
+        extensible-choice-parameter: {}
         gerrit-trigger: {}
         git: {}
         heavy-job: {}