Correct swift service name in docs

The docs incorrectly show an example of:

  enable_service swift

This does not work, it must be enabled on a per swift service
basis, like:

  enable_service s-proxy s-object s-container s-account

Change-Id: Ib4ed8b43f777d308f5464d45dc87735e843c0daf
Merge "Correct swift service name in docs"