Add repos only when there're packages for install

At the moment we allow not to install packages by providing
systemd_networkd_distro_packages as an empty list. When that happens
it makes sense also to skip all tasks related to adding repositories
when no packages are going to be installed.

Not installing packages might be useful for containers creation or
in situations when there is no networking yet, but we know that
systemd-networkd is already present.

Change-Id: I5e12cb0eb07b5eb8dcca462dbe8239a926ef80e6

tasks/main.yml

@@ -28,9 +28,13 @@
   tags:
     - always
 
-# Copy all factored-in GPG keys.
-# KeyID 2F86D6A1 from https://dl.fedoraproject.org/pub/epel/RPM-GPG-KEY-EPEL-8
-- name: If a keyfile is provided, copy the gpg keyfile to the key location
+- name: Install required repos and packages
+  when:
+    - systemd_networkd_distro_packages | length > 0
+  block:
+    # Copy all factored-in GPG keys.
+    # KeyID 2F86D6A1 from https://dl.fedoraproject.org/pub/epel/RPM-GPG-KEY-EPEL-8
+    - name: If a keyfile is provided, copy the gpg keyfile to the key location
       copy:
         src: "{{ item.keyfile }}"
         dest: "{{ item.key }}"
@@ -39,15 +43,15 @@
       when:
         - ansible_facts['os_family'] | lower == 'redhat'
 
-- name: Ensure GPG keys have the correct SELinux contexts applied
+    - name: Ensure GPG keys have the correct SELinux contexts applied
       command: restorecon -Rv /etc/pki/rpm-gpg/
       # TODO(evrardjp): Be more idempotent
       changed_when: false
       when:
         - ansible_facts['os_family'] | lower == 'redhat'
 
-# Handle gpg keys manually
-- name: Install gpg keys
+    # Handle gpg keys manually
+    - name: Install gpg keys
       rpm_key:
         key: "{{ key.key }}"
         validate_certs: "{{ key.validate_certs | default(omit) }}"
@@ -62,8 +66,8 @@
       when:
         - ansible_facts['os_family'] | lower == 'redhat'
 
-# NOTE(jrosser) this repo is configured with the path to the first gpg key provided
-- name: Install the EPEL repository
+    # NOTE(jrosser) this repo is configured with the path to the first gpg key provided
+    - name: Install the EPEL repository
       yum_repository:
         name: epel-networkd
         baseurl: "{{ systemd_networkd_epel_mirror ~ '/' ~ ansible_facts['distribution_major_version'] ~ '/Everything/' ~ ansible_facts['architecture'] }}"
@@ -80,15 +84,13 @@
       retries: 5
       delay: 2
 
-- name: Install networkd distro packages
+    - name: Install networkd distro packages
       package:
         name: "{{ systemd_networkd_distro_packages }}"
         state: "present"
         update_cache: "{{ (ansible_facts['pkg_mgr'] == 'apt') | ternary('yes', omit) }}"
         cache_valid_time: "{{ (ansible_facts['pkg_mgr'] == 'apt') | ternary(600, omit) }}"
         enablerepo: "{{ systemd_networkd_enablerepo | default(omit) }}"
-  when:
-    - systemd_networkd_distro_packages | length > 0
       register: install_packages
       until: install_packages is success
       retries: 3