Add ssh-slaves plugin

PROD-30944

Change-Id: Ic22732214f033c12e770922159ef3cdccca4f43d
diff --git a/Dockerfile b/Dockerfile
index 9c0c0db..1543e83 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -129,6 +129,7 @@
         simple-theme-plugin:0.5.1 \
         slack:2.3 \
         ssh-agent:1.17 \
+        ssh-slaves:1.29.4 \
         test-stability:2.3 \
         throttle-concurrents:2.0.1 \
         workflow-cps:2.58 \