validation: each test cases use different container id

[guni1192]

Hi

I'm validating my runtime by validation/kill/kill.t.

Testing result:

1. Test Case A(Pass): container is deleted after testing kill container
2. Test Case B(Fail): testing occur error when creating container. container-id is duplicated

When Test Case A could not delete container after testing, Test Case B occurred error(duplicate container id).
The reason is that both test cases are using same container id.

I propose that each test cases use different container id.