LU-16200 tests: test_32[f,g]: specify blocksize explicitly

LU-16200 tests: test_32[f,g]: specify blocksize explicitly

Fix conf-sanity:test_32f(), conf-sanity:test_32g() to be
independent from BLOCKSIZE environment variable.

To reproduce the failure, just run:
   BLOCKSIZE=4096 ONLY=32g sh conf-sanity.sh
  -total 36
  -total 64
  +total 16
  +total 9
   144115205289279502 -rw-r--r-- 1 0 0  1160 1550597702 README
   conf-sanity test_32g: @@@@@@ FAIL: list verification failed

Fixes: 3c1c462399 ("LU-1943 tests: Refresh conf-sanity 32[ab]")
Test-Parameters: trivial testlist=conf-sanity
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-11013
Reviewed-by: Vladimir Saveliev <vlaidimir.saveliev@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: Iaa07df8f5a9ba286ef5b3a5581b667cc7de63334
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48708
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alexander <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>