Add swift details to experimental-swift-logs.*

Zuul must be explicitly told in its layout file which jobs should have
swift parameters passed in. Start with experimental-swift-logs.* passing
in the swift creds name as 'logs'. This matches up with the existing
config-pep8 jobs we have in the experimental queue which is being used
for testing.

Change-Id: I4816befb67bd3c793a72b8fcd403366cb9a523d4