LU-7102 tests: fix replay-dual.sh test_26 for MDSCOUNT=1

LU-7102 tests: fix replay-dual.sh test_26 for MDSCOUNT=1

The replay-dual.sh test_26 code could never pass for MDSCOUNT=1
since it was returning a "false" condition for the first
conditional and always tripping the error message:

	[ $MDSCOUNT -ge 2 ] && {set default dirstripe} || error

Instead, make {set default dirstripe} a sub-clause of the conditional.

Fix cleanup_26 to kill proper dbench pid.

Clean up some code style in this test.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I0849318aa59e5698efb27b730a69e2f1b4e2d181
Reviewed-on: http://review.whamcloud.com/16414
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>