Stop sending underscores in header names to Swift

eventlet>=0.37.0 drops headers with underscores on the floor; as a
result, account and container metadata may not be stored properly.

See https://github.com/eventlet/eventlet/commit/ed743d75

Change-Id: Idcaacfed5e0203760e9cb2911d93700d8cb63cb5
2 files changed