LU-6095 tests: define TRUNCATE program for racer

LU-6095 tests: define TRUNCATE program for racer

In file_truncate.sh of racer, TRUNCATE was not defined for remote
clients. Let it point to tests/truncate in case it's not defined.

The same thing happens to MCREATE and LFS, fix them also and do
some cleanup.

Test-Parameters: alwaysuploadlogs testlist=racer
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: Ie6898f1573bd19810a2d8f14dc0aa375d3774e08
Reviewed-on: http://review.whamcloud.com/13501
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>