LU-4643 hsm: Make sanity-hsm test_60 more robust

LU-4643 hsm: Make sanity-hsm test_60 more robust

The first version of this test was fragile and could fail
intermittently when test infrastructure was not capable of
providing 1MB/sec in lustre bandwidth. This commit changes the
test to validate that a progress update occurs within the expected
window, rather than testing for a specific amount of data copied
under ideal conditions.

Signed-off-by: Michael MacDonald <michael.macdonald@intel.com>
Change-Id: Ief40a27452bc09d94101c7df00a46aa171a572f8