devstack: Revert setting SWIFT_REPLICAS
devstack: Revert setting SWIFT_REPLICAS

Setting SWIFT_REPLICAS=1 causes devstack to launch a performance
optimization for swift which includes launching swift in foreground.

But due to this ssh to cleanvm is not really closed causing jenkins to
wait for ever.

gosipyan/automation,SUSE-Cloud/automation,aspiers/automation,gosipyan/automation,gosipyan/automation,aspiers/automation,aspiers/automation,aspiers/automation,SUSE-Cloud/automation,SUSE-Cloud/automation,SUSE-Cloud/automation,gosipyan/automation