These XMLs live in a separate directory, there's no need for them
to have a special prefix in addition. It also doesn't play nicely
with ':e' completion in Vim, finding proper file based on
qemuxml2argvtest.c is also needlessly complicated.

The files were renamed using the following commands. From
qemuxml2argvdata:

  for i in qemuxml2argv-*.xml; do mv $i ${i#qemuxml2argv-}; done

and then (to fix broken symlinks) from qemuxml2argvdata and
qemuxml2xmloutdata:

  for i in $(find . -xtype l); do \
      ln -sf $(readlink $i | sed 's/qemuxml2argv-//') $i;
  done
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

Since the virStorageEncryptionPtr encryption; is a member of
 _virStorageSource it really should be allowed to be a subelement
of the disk <source> for various disk formats:

   Source{File|Dir|Block|Volume}
   SourceProtocol{RBD|ISCSI|NBD|Gluster|Simple|HTTP}

NB: Simple includes sheepdog, ftp, ftps, tftp

That way we can set up to allow the <encryption> element to be
formatted within the disk source, but we still need to be wary
from whence the element was read - see keep track and when it
comes to format the data, ensure it's written in the correct place.

Modify the qemuxml2argvtest to add a parse failure when there is an
<encryption> as a child of <disk> *and* an <encryption> as a child
of <source>.

The virschematest will read the new test files and validate from a
RNG viewpoint things are fine.