the wrapper is needed by transfer streams to restart a failed transfer
if desired. curlFileTransfer itself is more of a fancy handler for the
thread we're dedicating to curl io handling. the thread will stay with
the multi handle for now because quit handling needs to stay there. we
could have CurlMulti keep only a flag, but that does not help us much.
Change-Id: I99550f0bbb635b75898ca7260f08275df86050e3
eldritch horrors
18efc848fe