LU-3226 test: do some cleanup for sanity.sh test_43a/b

LU-3226 test: do some cleanup for sanity.sh test_43a/b

This patch includes the following minor fixes for sanity.sh
test_43a/b:
- to remove multiop after the current test and provide a clean env
for the next test;
- to do some style cleanup.

Test-Parameters: clientdistro=fc18 clientarch=x86_64 serverdistro=el6 serverarch=x86_64 testlist=sanity
Signed-off-by: Liu Ying <emoly.liu@intel.com>
Change-Id: I86221d9dbf1188b553b3c65bb14298e62f19f820
Reviewed-on: http://review.whamcloud.com/6414
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>