Allow for adjustment of RBD configuration options via Storage
Pool XML Namespace adjustments. When namespace arguments are
used to start the pool, add a VIR_WARN to indicate that the
startup was tainted by custom config_opts.

Based off original patch/concept:

https://www.redhat.com/archives/libvir-list/2014-May/msg00940.htmlSigned-off-by: NJohn Ferlan <jferlan@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

This test failed for two reasons:
* The uuid was missing from the input file
* The output file had the <name> in a different place from the actual output

The existing 'chap' XML logic was never used - just defined.  Rather than
try to insert a square peg into a round hole, blow it up and rewrite the
logic to follow the 'ceph' format.

Remove the former "chap.login" and "chap.passwd" fields and replace
with "chap.username" and "chap.secret" in _virStoragePoolAuthChap.
Adjust the virStoragePoolDefParseAuthChap() to process.

Change the rng file to describe the new layout

Update the formatstorage.html to describe the usage of the secret element
to mention that the secret type "iscsi" and "ceph" can be used
to storage pool too.

Update the formatsecret.html to include a reference to the storage pool

Update tests to handle the changes from 'login' and 'passwd' to 'username'
and '<secret>' format

This patch adds support for a new storage backend with RBD support.

RBD is the RADOS Block Device and is part of the Ceph distributed storage
system.

It comes in two flavours: Qemu-RBD and Kernel RBD, this storage backend only
supports Qemu-RBD, thus limiting the use of this storage driver to Qemu only.

To function this backend relies on librbd and librados being present on the
local system.

The backend also supports Cephx authentication for safe authentication with
the Ceph cluster.

For storing credentials it uses the built-in secret mechanism of libvirt.
Signed-off-by: NWido den Hollander <wido@widodh.nl>