Verify ansible 2.8 is used

ansible/bootstrap.yml

@@ -6,10 +6,9 @@
     - name: Require minimal ansible version
       assert:
         that:
-          - "ansible_version.full is version_compare('2.7', '>=')"
-          - "ansible_version.full is version_compare('2.8', '<')"
+          - "ansible_version.full is version_compare('2.8', '>=')"
         msg: >
-          "Please use Ansible 2.7.x to bootstrap your OAS cluster."
+          "Please use Ansible 2.8.x to bootstrap your OAS cluster."
 
     - name: Release name must start with lower case
       assert: