Add delay in swift-bench

With enable write affinity, it's necessary to wait until
replication has moved things to their proper homes before
running delete request. With write affinity turned on, only
nodes in local region will get the object right after PUT request.

Fix bug #1198926

Change-Id: I3aa8933d45c47a010ae05561e12176479e7c9bcc
Merge "Add delay in swift-bench"