https://bugzilla.redhat.com/show_bug.cgi?id=1572491

Commit id '78661cb1' added a physical output, but failed to update
the schema resulting in a failure from virt-xml-validate.

While at it - update the storagevolschemadata for the output.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>
ACKed-by Michal Privoznik <mprivozn@redhat.com>

We don't parse it anyway.

https://bugzilla.redhat.com/show_bug.cgi?id=893273

The XML allows <encryption format='unencrypted'/>, this implementation
canonicalizes the internal representation so that "vol->encryption" is
non-NULL iff the volume is encrypted.

Note that partial encryption information (e.g. specifying an encryption
format, but not the key/passphrase) is valid, libvirt will automatically
choose value for the missing information during volume creation.  The
user can read the volume XML, and use the unmodified <encryption> tag in
future operations (without having to be able to understand) its contents.

* docs/formatstorage.html, docs/formatstorage.html.in: Document
  storage volume encryption options
* src/storage_conf.c, src/storage_conf.h: Hook up storage
  encryption XML handling
* tests/storagevolschemadata/vol-qcow2.xml: Test case for encryption
  schema changes

* docs/schemas/storagevol.rng docs/formatstorage.html[.in]
  tests/storagevolschemadata/vol-qcow2.xml: fix storage volume
  inconsistencies in schema and document, patch by Ryota Ozaki
daniel