LU-4819 tests: Lustre Sanity test_101b hangs for large OSTCOUNTs

LU-4819 tests: Lustre Sanity test_101b hangs for large OSTCOUNTs

sanity.sh test_101b hangs during Lustre sanity test. This
is happening especially in cases where the $OSTCOUNT is
greater than 100.

Due to OSTCOUNT of more than 100, the ITERATION parameter
results in '0', which causes the 'reads' utility to run
in infinite 'for' loop. Thus resulting in a hang on such
setups.

This change would make necessary changes in FILE_LENGTH in
test_101b and its related routines(setup_101bc, ra_check)
so that, the test won't hang and would proceed rightly.

Signed-off-by: Parinay Kondekar <parinay_kondekar@xyratex.com>
Change-Id: I0815dfd8777d3055cf5dd6de01b2a18d1bff96bf
Xyratex-bug-id: MRP-1362
Reviewed-on: http://review.whamcloud.com/9788
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>