examples: Correct the example command to use testnode.xml

 * s/-connection/-c/
 * Removes the redundant '/'.
 * Add "absolute" so that it's more clear.

Pushed under trivial rule.

examples/xml/test/testnode.xml

@@ -4,7 +4,7 @@
      of applications using libvirt. To use this with virsh, run something
      like:
 
-      virsh -connect test:////path/to/this/dir/testnode.xml nodeinfo
+      virsh -c test://absolute/path/to/this/dir/testnode.xml nodeinfo
 
      -->
   <domain file="testdomfv0.xml"/>