LU-3096 tests: combine dependent sanity tests

LU-3096 tests: combine dependent sanity tests

Some tests can not run as expected when previous dependent test is not
ran.
This patch combines the following sanity tests:
    test 4 is removed as duplicate of test 1
    tests 6a, 6b to test 6a
    tests 6c, 6d to test 6c
    tests 6e, 6f to test 6e
Test 0 is renamed to test 0a to allow running it separately.

Signed-off-by: Vladimir Saveliev <vladimir_saveliev@xyratex.com>
Xyratex-bug-id: MRP-814
Change-Id: I4cc2a18ec7a95f5b0a3a67ff799077689d2e30d1
Reviewed-on: http://review.whamcloud.com/5929
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>