Merge pull request #3351 from edx/jibsheet/other-tools-edx-jenkins-plugins

We need gradle to run tests and to install libs for seed jobs

playbooks/roles/tools_jenkins/defaults/main.yml

@@ -42,3 +42,5 @@ jenkins_tools_plugins:
   - { name: "github", version: "1.21.1" }
   - { name: "plain-credentials", version: "1.2" }
   - { name: "github-oauth", version: "0.24" }
+  - { name: "gradle", version: "1.25" }
+  - { name: "credentials-binding", version: "1.9" }