Revert "Raise VimFaultException for unknown faults"

This reverts commit 1668fef9ca

This is a backwards incompatible change, as we see with the
nova driver code that is expecting a VMwareDriverException
but is now getting back a VimFaultException because the unit
tests in nova were passing an unknown fault class name.

Change-Id: I0f8042c6e47f6eb9802e770ffb7d09bdbe57013b
Closes-Bug: #1459021

oslo_vmware/exceptions.py

@@ -254,6 +254,7 @@ def get_fault_class(name):
     fault_class = _fault_classes_registry.get(name)
     if not fault_class:
         LOG.debug('Fault %s not matched.', name)
+        fault_class = VMwareDriverException
     return fault_class