Making order in tests.
    
    --removed duplicated test-io
    --reusing library libsss_test_common in other tests
    --cmocka test sss_nss_idmap-tests was moved to cmocka dir
    --moved leak_check.c to libsss_test_common
    --moved common_tev.c,common_dom.c to libsss_test_common
      (leak_check.c,common_tev.c,common_dom.c) are test framework independent