ansible: Change all our group names from foo-bar to foo_bar or foo-bar-baz to foo_bar_baz

In ansible 2.8 the - character isn't supposed to be valid in group names.
While we could override this, might has well just bite the bullet and change it.
So, just switch all group names to use _ instead of -

Signed-off-by: Kevin Fenzi <kevin@scrye.com>

playbooks/groups/maintainer-test.yml

@@ -1,5 +1,5 @@
 - name: Spin up maintainertest cloud instances
-  hosts: maintainer-test
+  hosts: maintainer_test
   gather_facts: False
 
   vars_files:
@@ -12,7 +12,7 @@
   - import_tasks: "{{ tasks_path }}/persistent_cloud.yml"
 
 - name: Do some basic cloud setup on them
-  hosts: maintainer-test
+  hosts: maintainer_test
   gather_facts: True
   vars_files:
    - /srv/web/infra/ansible/vars/global.yml
@@ -36,7 +36,7 @@
 - import_playbook: "/srv/web/infra/ansible/playbooks/include/virt-create.yml myhosts=aarch64-test"
 
 - name: Setup maintainer test hosts
-  hosts: arm-packager:maintainer-test:aarch64-test
+  hosts: arm_packager:maintainer_test:aarch64_test
   gather_facts: True
   tags:
    - maintainer-test