LU-16027 tests: sanity:test_66: specify blocksize explicitly

LU-16027 tests: sanity:test_66: specify blocksize explicitly

Fix test_66() to be independent from BLOCKSIZE environment
variable.

To reproduce the failure, just run:
  llmount.sh
  export BLOCKSIZE=4096; ONLY=66 sh sanity.sh
  == sanity test 66: update inode blocks count on client ==
  8+0 records in
  8+0 records out
  8192 bytes (8.2 kB, 8.0 KiB) copied, 0.00589935 s, 1.4 MB/s
  sanity test_66: @@@@@@ FAIL: /mnt/lustre/f66 blocks 2 < 8

Test-Parameters: trivial testlist=sanity env=ONLY=66
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-11014
Reviewed-by: Vladimir Saveliev <vlaidimir.saveliev@hpe.com>
Change-Id: I0adca724518cb955e3664d33a36628ae19a1712d
Reviewed-on: https://review.whamcloud.com/47983
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>