stress_memory_heavy: Add memory stress case

This stress tests is for background test as memory stress.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
stress_memory_heavy: Change import client.bin to client

Bin folder has been removed and most file in it have been moved to
client folder.

Signed-off-by: Feng Yang <fyang@redhat.com>