Handle non-existent item when calling update_item

If update_item action(s) is(are) ADD and/or PUT, a new item
will be created if expected conditions are satisfied. Otherwise
ConditionalCheckFailedException will be thrown. If
action(s) is(are) DELETE only, no operation will be performed
and a success response will be returned.

Closes-Bug: #1373627

Change-Id: Ib58d1433dd546f1472129b669f14a1b689647e1d
Merge "Handle non-existent item when calling update_item"
Add 'last_updated' to 'table_info'

Update table status to *_FAILED if it stucks
to CREATING/DELETING state for a long time

Implements blueprint: table-info-timestamp

Change-Id: I03659858285082e3eca88846bea3c8fb7a3009cf