put item does not replaces item with predefined attributes

[Andrei V. Ostapenko]

In the table with predefined attributes, that are not used in primary key put item does not replace item properly.

Bug replay:

1. Create a table with 3 attributes. 2 of them will be used in key schema
2. Put an item, that contains all 3 attributes
3. Put an item with two attributes (just the same key schema as in 1st item)
4. Get this item - you will receive an item with all 3 attributes, however expected is to receive just 2.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/119462

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/119462
Committed: https://git.openstack.org/cgit/stackforge/magnetodb/commit/?id=f3396b9bd2d1a80fee279533716e24c19b79433b
Submitter: Jenkins
Branch: master

commit f3396b9bd2d1a80fee279533716e24c19b79433b
Author: Andrei V. Ostapenko <email address hidden>
Date: Fri Sep 5 16:10:29 2014 -0400

    Fixes bug with put item predefined attributes

    Fixes bug that prevents setting to 'null' item
    predefined attributes, that are not mentioned
    in put request.

    Closes-bug: #1348336
    Change-Id: I5ad0db7ea81224c2a6f42a4f792f1dbf28f85c90