Improve integration tests which run with PaxExam.

  * Don't use @BeforeClass and @AfterClass.
  * Run all tests in one test container in order to shorten test time.

Change-Id: I09618b99c409261e6ccf17ecc8773576f90c851a
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>