Bug 1383491, Some problems remaining with incorrect ESP boundaries

When making up missing columns from HBase split keys that are
shorter than the actual key, there were a couple of issues:

These keys were created as decoded key values, but the code
below decoded them a second time.

Also, the code did not handle nullable columns properly.

These two fixes also solved the remaining issue with interval columns,
mentioned in bug 1375902.

Change-Id: Ie311fcc33c1a6920b68227fc2fff43a386f3c2e8
Merge "Bug 1383491, Some problems remaining with incorrect ESP boundaries"