Remove lockfile from requirements
Remove lockfile from requirements

It's not used nor imported by the project directly and Horizon switched
to oslo.concurrency.

Change-Id: Ib6f8703837bb5360bb0c481dadb606463d3163d3

rdo-management/tuskar-ui,rdo-management/tuskar-ui,rdo-management/tuskar-ui,rdo-management/tuskar-ui