LU-3000 tests: several fixes of tests for DNE

1. sanity 27u, set PRECREATE_FAIL for every MDS.

2. sanity 133d, use mkdir, instead of test_mkdir to
avoid checking rename stats on remote MDTs.

3. conf-sanity 32, use do_rpc_nodes for reload module,
in case it needs to reload module on remote nodes, and
also umount mdt2 in 32c.

4. conf-sanity 42, add load_modules to avoid missing
module errors in some cases.

5. skip test_53 and test_225 when there are more than
one MDT.

6. redirect error message to /dev/null, to avoid
too much error message in the log, which might
explore the size of the log.

Test-parameters: mdscount=2 mdtcount=2 testlist=sanity,conf-sanity

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: Ic09d97fb68b923b3a5862371a59c5ba655c278a7
Reviewed-on: http://review.whamcloud.com/5877
Reviewed-by: Li Wei <wei.g.li@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>