Increase max servers in pool main

Change-Id: Ifc482ca2cf695fb3b60adcb98aa4da3896823a2c
diff --git a/nodepool/nodepool.yaml b/nodepool/nodepool.yaml
index 852dc24..56ba3de 100644
--- a/nodepool/nodepool.yaml
+++ b/nodepool/nodepool.yaml
@@ -72,7 +72,7 @@
         username: ubuntu
     pools:
       - name: main
-        max-servers: 4
+        max-servers: 6
         auto-floating-ip: False
         networks:
           - lab-untrusted-access