virsh: Fix man page argument ordering for vol-{path|name|key} commands

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

tools/virsh.pod

@@ -4232,24 +4232,34 @@ information.
 
 If the I<--uuid> option is given, the pool UUID is returned instead.
 
-=item B<vol-path> [I<--pool> I<pool-or-uuid>] I<vol-name-or-key>
+=item B<vol-path> I<vol-name-or-key> [I<--pool> I<pool-or-uuid>]
 
 Return the path for a given volume.
+
+I<vol-name-or-key> is the name or key of the volume to return the path.
+
 I<--pool> I<pool-or-uuid> is the name or UUID of the storage pool the volume
-is in.
-I<vol-name-or-key> is the name or key of the volume to return the path for.
+is in. If the volume name is provided instead of the key, then providing
+the pool is necessary to find the volume to be uploaded into; otherwise,
+the first volume found by the key will be used.
 
 =item B<vol-name> I<vol-key-or-path>
 
 Return the name for a given volume.
-I<vol-key-or-path> is the key or path of the volume to return the name for.
 
-=item B<vol-key> [I<--pool> I<pool-or-uuid>] I<vol-name-or-path>
+I<vol-key-or-path> is the key or path of the volume to return the name.
+
+=item B<vol-key> I<vol-name-or-path> [I<--pool> I<pool-or-uuid>]
 
 Return the volume key for a given volume.
+
+I<vol-name-or-path> is the name or path of the volume to return the
+volume key.
+
 I<--pool> I<pool-or-uuid> is the name or UUID of the storage pool the volume
-is in. I<vol-name-or-path> is the name or path of the volume to return the
-volume key for.
+is in. If the volume name is provided instead of the path, then providing
+the pool is necessary to find the volume to be uploaded into; otherwise,
+the first volume found by the path will be used.
 
 =item B<vol-resize> I<vol-name-or-path> I<capacity> [I<--pool> I<pool-or-uuid>]
 [I<--allocate>] [I<--delta>] [I<--shrink>]