Add API to enable calling module to register an exception

In certain cases the application, for example Nova, may need to treat
a VC exception that is currently not supported by oslo.vmware.

This will enable the application to dynamically add exceptions and then
remove them when oslo.vmware is updated to support the new exception.

The patch also fixes a typo with the exception fault handling.

Change-Id: I332a4ff2ac2c6d4e6ac88bbd067ef0d4e659ffa3
Merge "Add API to enable calling module to register an exception"