Let swift-object-info skip etag verification

Now swift-object-info has a "-n" option that will cause the etag
verification to be skipped; on large objects, the etag verification
takes the vast majority of the runtime, and sometimes you just want to
know which account owns the 5 GB monstrosity without waiting around while
its checksum is verified.

Change-Id: Id284570633eb7b98046cdb948d7c37a152de1195
Merge "Let swift-object-info skip etag verification"