VMware: provide a coherent message to user when viewing console log

The vCenter and ESX returns a PNG format. Currently there is no way
to display a text based format. This at least provides the user with
a message that is informative.

Fixes bug: 1199754

Change-Id: I382219ca89a1574ca233b0f25a89af63af71a22f
Merge "VMware: provide a coherent message to user when viewing console log"