Adds tempest tests to cover update_item functionality

Adds negative tests on update item from nonexistent and
creating table.
Adds negative tests on update item with wrong expected
parameter.
Adds negative tests on update item with invalid and empty
key.

Partially implements: bp increase-tempest-test-coverage
Change-Id: I9d793f0a6f27ca6cad8568ee07f96926748b4074
Merge "Adds tempest tests to cover update_item functionality"