Fixed row deletion for deleted stack

Now heat returns stack with "stack_status == 'DELETE_COMPLETE'"
for deleted stack. Added corresponding check to ajax handler.

HTTPNotFound is not used anymore and deprecated. Removed except
block for it.

Added raise to generic "except Exception" block to prevent
internal errors inside horizon.

Change-Id: Ia9cfd975790872918ba25c347319003ddc3468fa
Closes-Bug: #1367758
Merge "Fixed row deletion for deleted stack"