nodepool: use the same security groups for the MAAS nodes

It seems that default + "Remote Access" is not enough even for
incoming SSH connections.

Change-Id: I86ade3a079d258bc1678bc6d835eddabc61c625c
diff --git a/nodepool/nodepool.yaml b/nodepool/nodepool.yaml
index fe64edf..9a44c22 100644
--- a/nodepool/nodepool.yaml
+++ b/nodepool/nodepool.yaml
@@ -70,8 +70,8 @@
       - name: zaza-main
         auto-floating-ip: False
         security-groups:
+          - pp-net
           - "Remote Access"
-          - default
         networks:
           - lab-charmed-testing-ssh
         labels: