Fix a cycle in graph of tasks

This patch removes a dependency that causes a cycle in the graph of
tasks in MOS 8. The cycle was <custom>-netconfig -> hosts -> cluster
-> virtual_ips -> <custom>-netconfig.

We cannot remove hosts.pp as we tried previously because doing this also
remove a dependency between globals and hosts. So we create the
following dependency:

tools -> <custom>-netconfig -> hosts

in place of the former:

tools -> netconfig -> hosts

Partial-Bug: #1616391
Change-Id: I67abb9f45a0156017236defb04196c701f75926b

deployment_tasks.yaml

@@ -67,12 +67,19 @@
   reexecute_on:
     - deploy_changes
 
-# We cannot use the legacy 'netconfig' task because it won't create the proper
-# dependency on the virtual management router task.
+# We cannot use the legacy 'netconfig' task because with MOS 9, it won't create
+# the proper dependency on the 'virtual_ips' task for the InfluxDB-Grafana
+# nodes. As a consequence, the deployment will fail because the nodes will
+# perform operations that download stuff from the Internet (like running
+# 'apt-get update') while the virtual router isn't ready yet. For MOS 8, the
+# task depends on the 'tools' task and not on the 'virtual_ips' task otherwise
+# it creates a dependency cycle. In this case, this isn't an issue because the
+# default gateway is only changed at post-deployment (see the
+# 'influxdb-configure-default-route' task).
 - id: influxdb-netconfig
   type: puppet
   version: 2.0.0
-  requires: [influxdb-hiera, virtual_ips]
+  requires: [influxdb-hiera, tools]
   required_for: [deploy_end, hosts]
   cross-depends:
     - name: virtual_ips