pikvm: Add role/playbook for PiKVM

PiKVM comes with its own custom Arch Linux-based operating systems.  We
want to be able to manage it with our configuration policy, especially
for setting up authentication, etc.  It won't really work with the
host-provisioner without some pretty significant changes to the base
playbooks, but we can control some bits directly.

pikvm.yml

@@ -0,0 +1,19 @@
+- hosts: pikvm
+  pre_tasks:
+  - name: remount rootfs read-write
+    command: rw
+    tags:
+    - remount-rw
+    - remount
+  roles:
+  - role: hostname
+  - role: base
+  - role: pikvm
+    tags:
+    - pikvm
+  tasks:
+  - name: remount rootfs read-only
+    command: ro
+    tags:
+    - remount-ro
+    - remount