Return VixDiskLib Load Error to DRB Client

When VixDiskLibServer fails to successfully load any
version of the VixDiskLib, cache the failure reason.  
Interrogate for the error once the DRB service is started 
so that the failure reason can be passed back to the client 
for presentation in the UI. Then shut down the DRB service.

@roliveri, @jrafanie, @chessbyte please review
Also, do we have different messages to differentiate between failing to load any version of the library, and failing because we loaded an unsupported version (5.1.0)? Is that distinction only made in the log messages? I think it would be useful to convey that difference to the client as well.