vRouter install docs need updating

The guide for configuring vRouter on a physical POD uses the old method of uploading the fabric config to the TOSCA engine.  This method does not work with the new engine in 5.0:

https://guide.opencord.org/cord-5.0/vrouter.html#interface-configuration

Instead the "make fabric-refresh" target is used as described here:

https://guide.opencord.org/cord-5.0/vrouter.html#interface-configuration

Note that the new target does not save the generated config to a file on the host where it can be edited.  In order to manually modify the config it's necessary to use the XOS GUI.