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
Currently no.  We attempt to load each possible version of the library until we succeed. Whether it fails because the version isn't installed, or because of an unsupported version, we still try the next one in the list under the assumption that there might be more than one version available.  If this assumption is valid, we wouldn't know which of the failures is the relevant one to return.  We could however return a concatenated string of all the unsupported version failures. If the assumption is invalid (which it very well may be) we can return the reason for the first unsupported version.