Merge BadRequest tests of "attach interfaces" API

In test_attach_interfaces, there are BadRequest tests of "attach interfaces".
Most parts of them are duplicated.
This patch merges them for the readability and clarifying their purposes.

Change-Id: Ib9dd2840be46dec6b70fe9e3fda35de88f84b4a9
Merge "Merge BadRequest tests of "attach interfaces" API"