Unskip test_stack_update_add_remove()

test_stack_update_add_remove was skipped because of bug 1308682 which
is now in a state which should allow us to unskip it.

Change-Id: I9b728abe3432f61f883d50b4a9d7d8d9c2b1f8b2
Related-Bug: #1308682
Merge "Unskip test_stack_update_add_remove()"