vmem drivers should handle client library imports and failures better

[Ryan Lucio]

During review for a fix to the violin drivers #1430009 (https://review.openstack.org/164942) it was suggested that I find a better way to import the company specific client library, so that if it fails then the driver will handle that nicely (ie., not just ignoring the error and then throwing an exception on the first attempt to use a library class/function). Suggestions for a best practice so far have centered around checking the result of the import during check_for_setup_error().

The goal would be to survey other drivers and consider best practices, implement that in the vmem drivers, and then propose it to the core group as a potential addition to the dev guide.

[Sean McGinnis (sean-mcginnis)]

Automatically unassigning due to inactivity.