virsh: Fix man page argument ordering for vol-clone command

The proper command order is 'virsh vol-clone source-vol target-vol pool'.
While making the modification clean up the description a bit too in
order to help clarify under what circumstances the source-vol could be
found if the pool name was not provided.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

tools/virsh.pod

@@ -4032,19 +4032,27 @@ support full allocation). This option creates a sparse image file with metadata,
 resulting in higher performance compared to images with no preallocation and
 only slightly higher initial disk space usage.
 
-=item B<vol-clone> [I<--pool> I<pool-or-uuid>] I<vol-name-or-key-or-path>
-I<name> [I<--prealloc-metadata>] [I<--reflink>]
+=item B<vol-clone> I<vol-name-or-key-or-path> I<name>
+[I<--pool> I<pool-or-uuid>] [I<--prealloc-metadata>] [I<--reflink>]
 
 Clone an existing volume within the parent pool.  Less powerful,
 but easier to type, version of B<vol-create-from>.
-I<--pool> I<pool-or-uuid> is the name or UUID of the storage pool
-that contains the source volume, and will contain the new volume.
+
 I<vol-name-or-key-or-path> is the name or key or path of the source volume.
+
 I<name> is the name of the new volume.
+
+I<--pool> I<pool-or-uuid> is the name or UUID of the storage pool
+that contains the source volume and will contain the new volume.
+If the source volume name is provided instead of the key or path, then
+providing the pool is necessary to find the volume to be cloned; otherwise,
+the first volume found by the key or path will be used.
+
 [I<--prealloc-metadata>] preallocate metadata (for qcow2 images which don't
 support full allocation). This option creates a sparse image file with metadata,
 resulting in higher performance compared to images with no preallocation and
 only slightly higher initial disk space usage.
+
 When I<--reflink> is specified, perform a COW lightweight copy,
 where the data blocks are copied only when modified.
 If this is not possible, the copy fails.