Increase minimal Ansible version to 2.8

ansible-freeipa is a new Ansible Collection introduced with Ansible 2.8 and
Ansible Galaxy 3.2.

roles/ipaclient/meta/main.yml

@@ -5,7 +5,7 @@ galaxy_info:
   description: A role to join a machine to an IPA domain
   company: Red Hat, Inc
   license: GPLv3
-  min_ansible_version: 2.5.0
+  min_ansible_version: 2.8
   platforms:
   - name: Fedora
     versions:
@@ -13,7 +13,7 @@ galaxy_info:
   - name: EL
     versions:
     - 7
-    # - 8
+    - 8
   galaxy_tags:
     - identity
     - ipa