Add condition to os-net-config run during upgrade.

This add two conditionals:
 - first check that os-net-config needs upgrade
 - second verify that the configuration file exist and non empty.

This prevent unnecessary run of os-net-config and error in certain
network configuration.

Change-Id: Ic905f7ed7e7fc9018bc494f77811392045fddfe8
Closes-Bug: #1730328

puppet/services/tripleo-packages.yaml

@@ -53,6 +53,16 @@ outputs:
           fail: msg="rpm-python package was not present before this run! Check environment before re-running"
           when: rpm_python_check.changed != false
           tags: step0
+        - name: Check for os-net-config upgrade
+          shell: yum check-upgrade | grep os-net-config
+          register: os_net_config_need_upgrade
+          ignore_error: True
+          tags: step3
+        - name: Check that os-net-config has configuration
+          shell: test -s /etc/os-net-config/config.json
+          register: os_net_config_has_config
+          ignore_error: True
+          tags: step3
         - block:
             - name: Upgrade os-net-config
               yum: name=os-net-config state=latest
@@ -62,6 +72,7 @@ outputs:
               failed_when: os_net_config_upgrade.rc not in [0,2]
               changed_when: os_net_config_upgrade.rc == 2
           tags: step3
+          when: not os_net_config_need_upgrade.stdout and os_net_config_has_config.rc == 0
         - name: Update all packages
           tags: step3
           yum: name=* state=latest