THe swift backend was using swiftclient.Connection without any checks,
but that object is not thread safe, so we need to only have one
instance. This adds a wrapper to keep the same API but not share any
data.
Change-Id: Ic8152f8f7cb6d4d0b4ab473d2f937a9bc77b8453
(cherry picked from commit 80f8ca818a)