This is missing on the newest docker images

From resurrecting old docker images, it appears that we got it for
"free" as part of the jenkins container, but don't have it now that
we're starting from a clean install.

playbooks/roles/tools_jenkins/defaults/main.yml

@@ -46,6 +46,7 @@ jenkins_tools_plugins:
   - { name: "github-oauth", version: "0.24" }
   - { name: "gradle", version: "1.25" }
   - { name: "credentials-binding", version: "1.9" }
+  - { name: "envinject", version: "1.92.1" }
 
 # ec2 + dependencies, used by the android build workers + any additional workers we build
   - { name: "ec2", version: "1.36" }