LU-11498 tests: remove duplicate write_disjoint test name

LU-11498 tests: remove duplicate write_disjoint test name

Patch renames write_disjoint() test added by LU-9409 / LUS-1705
to write_disjoint_tiny() to keep the tests names unique.

Test-Parameters: trivial testlist=parallel-scale envdefinitions=ONLY="write_disjoint write_disjoint_tiny"
Signed-off-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-5939
Reviewed-by: Vladimir Saveliev <c17830@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Change-Id: I87961e244c5f3fcfdae8263591d03685d8d4fcbd
Reviewed-on: https://review.whamcloud.com/33343
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>