AttachInterfacesTest: use build_timeout on iterface deletion

Currently the test uses 5 seconds timeout.
This patch changes it to use configured build_timeout
in interface deletion check

Change-Id: I634fcc34365c79cee7282e7094177b9f37e16d2a
Related-Bug: #1265501
Merge "AttachInterfacesTest: use build_timeout on iterface deletion"