Remove the deprecated ibmnas driver

Remove the deprecated ibmnas driver

The ibmnas driver has been deprecated since the Liberty release.
In the Liberty release, NFS capabilities were added to the IBM
GPFS driver with commit:  bf4ca3bcf099760ef145571b975badc80d42b2d6 .
The ability for the GPFS driver to use NFS based shares rendered
the ibmnas driver redundant.

This commit removes the ibmnas driver and its tests.  The commit also
updates the opts.py file to remove reference to the ibmnas options.

Release notes are included with this commit.

DocImpact

Change-Id: Iac4a2f1770f7d02979eec1d8d5866d9fc4b6d18c