docs: Fix some minor issues with formatdomain docs

Item redundancy, some forgotten extra blank lines, etc.
Signed-off-by: NZhiPeng Lu <luzhipeng@uniudc.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

docs/formatdomain.html.in

@@ -2836,7 +2836,6 @@
     </source>
     <target dev='sdb' bus='scsi'/>
   </disk>
-  </disk>
   <disk type='network' device='lun'>
     <driver name='qemu' type='raw'/>
     <source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/0'>
@@ -5217,7 +5216,6 @@
     <virtualport>
       <parameters instanceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/>
     </virtualport>
-
   </interface>
 </devices>
 ...</pre>
@@ -5710,8 +5708,7 @@ qemu-kvm -net nic,model=? /dev/null
       &lt;host csum='off' gso='off' tso4='off' tso6='off' ecn='off' ufo='off' mrg_rxbuf='off'/&gt;
       &lt;guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/&gt;
     &lt;/driver&gt;
-    </b>
-  &lt;/interface&gt;
+    </b>&lt;/interface&gt;
 &lt;/devices&gt;
 ...</pre>
 
@@ -6213,7 +6210,7 @@ qemu-kvm -net nic,model=? /dev/null
     <b>&lt;route family='ipv4' address='192.168.122.0' prefix='24' gateway='192.168.122.1'/&gt;</b>
     <b>&lt;route family='ipv4' address='192.168.122.8' gateway='192.168.122.1'/&gt;</b>
   &lt;/hostdev&gt;
-
+  ...
 &lt;/devices&gt;
 ...
 </pre>