docs: use unique dev names in <disk> examples

Jiri Moskovcak reported on IRC that the documentation on valid
<disk> was confusing because it didn't have unique dev='...'
entries.

* docs/formatdomain.html.in: Use unique names.
Signed-off-by: NEric Blake <eblake@redhat.com>

docs/formatdomain.html.in

@@ -1555,14 +1555,14 @@
       <source protocol="rbd" name="image_name2">
         <host name="hostname" port="7000"/>
       </source>
-      <target dev="hdd" bus="ide"/>
+      <target dev="hdc" bus="ide"/>
       <auth username='myuser'>
         <secret type='ceph' usage='mypassid'/>
       </auth>
     </disk>
     <disk type='block' device='cdrom'>
       <driver name='qemu' type='raw'/>
-      <target dev='hdc' bus='ide' tray='open'/>
+      <target dev='hdd' bus='ide' tray='open'/>
       <readonly/>
     </disk>
     <disk type='network' device='cdrom'>
@@ -1570,7 +1570,7 @@
       <source protocol="http" name="url_path">
         <host name="hostname" port="80"/>
       </source>
-      <target dev='hdc' bus='ide' tray='open'/>
+      <target dev='hde' bus='ide' tray='open'/>
       <readonly/>
     </disk>
     <disk type='network' device='cdrom'>
@@ -1578,7 +1578,7 @@
       <source protocol="https" name="url_path">
         <host name="hostname" port="443"/>
       </source>
-      <target dev='hdc' bus='ide' tray='open'/>
+      <target dev='hdf' bus='ide' tray='open'/>
       <readonly/>
     </disk>
     <disk type='network' device='cdrom'>
@@ -1586,7 +1586,7 @@
       <source protocol="ftp" name="url_path">
         <host name="hostname" port="21"/>
       </source>
-      <target dev='hdc' bus='ide' tray='open'/>
+      <target dev='hdg' bus='ide' tray='open'/>
       <readonly/>
     </disk>
     <disk type='network' device='cdrom'>
@@ -1594,7 +1594,7 @@
       <source protocol="ftps" name="url_path">
         <host name="hostname" port="990"/>
       </source>
-      <target dev='hdc' bus='ide' tray='open'/>
+      <target dev='hdh' bus='ide' tray='open'/>
       <readonly/>
     </disk>
     <disk type='network' device='cdrom'>
@@ -1602,7 +1602,7 @@
       <source protocol="tftp" name="url_path">
         <host name="hostname" port="69"/>
       </source>
-      <target dev='hdc' bus='ide' tray='open'/>
+      <target dev='hdi' bus='ide' tray='open'/>
       <readonly/>
     </disk>
     <disk type='block' device='lun'>
@@ -1616,12 +1616,12 @@
       <source dev='/dev/sda'/>
       <geometry cyls='16383' heads='16' secs='63' trans='lba'/>
       <blockio logical_block_size='512' physical_block_size='4096'/>
-      <target dev='hda' bus='ide'/>
+      <target dev='sdb' bus='ide'/>
     </disk>
     <disk type='volume' device='disk'>
       <driver name='qemu' type='raw'/>
       <source pool='blk-pool0' volume='blk-pool0-vol0'/>
-      <target dev='hda' bus='ide'/>
+      <target dev='sdc' bus='ide'/>
     </disk>
     <disk type='network' device='disk'>
       <driver name='qemu' type='raw'/>
@@ -1641,7 +1641,7 @@
       <auth username='myuser'>
         <secret type='iscsi' usage='libvirtiscsi'/>
       </auth>
-      <target dev='sda' bus='scsi'/>
+      <target dev='vdb' bus='scsi'/>
     </disk>
     <disk type='volume' device='disk'>
       <driver name='qemu' type='raw'/>
@@ -1649,7 +1649,7 @@
       <auth username='myuser'>
         <secret type='iscsi' usage='libvirtiscsi'/>
       </auth>
-      <target dev='vda' bus='virtio'/>
+      <target dev='vdc' bus='virtio'/>
     </disk>
     <disk type='volume' device='disk'>
       <driver name='qemu' type='raw'/>
@@ -1657,7 +1657,7 @@
       <auth username='myuser'>
         <secret type='iscsi' usage='libvirtiscsi'/>
       </auth>
-      <target dev='vda' bus='virtio'/>
+      <target dev='vdd' bus='virtio'/>
     </disk>
     <disk type='file' device='disk'>
       <driver name='qemu' type='qcow2'/>
@@ -1671,7 +1671,7 @@
           <backingStore/>
         </backingStore>
       </backingStore>
-      <target dev='vda' bus='virtio'/>
+      <target dev='vde' bus='virtio'/>
     </disk>
   </devices>
   ...</pre>