Don't try to set pool limits on libvirt key

I figured a * wildcard would work, but no it doesn't. Libvirt needs
the ability to talk to any pool arbitrarily since PVC can create and
remove them at will.

roles/pvc/tasks/libvirt/bootstrap.yml

@@ -1,3 +1,3 @@
 ---
 - name: create Libvirt keyring
-  command: ceph auth get-or-create client.libvirt mon 'allow r' osd 'allow class-read object_prefix rbd_children, allow rwx pool=*'
+  command: ceph auth get-or-create client.libvirt mon 'allow r' osd 'allow class-read object_prefix rbd_children, allow rwx'