VMware: VimException __str__ attempts to concatenate string to list

Forces the correct parameter use in VimException and VimFaultException
both exceptions have similar signatures but very different uses. This
change forces a developer to deal with misuse of the exceptions
early in their development cycle (provided the do due dilligence with
their testing.)

Closes-bug: 1287884

Change-Id: I34753382677e3315ea4a71cfe9b3b82e9f9159bb
Merge "VMware: VimException __str__ attempts to concatenate string to list"