Currently the swiftclient logs sensitive info in headers when logging
HTTP requests. This patch hides sensitive info in headers such as
'X-Auth-Token' in a similar way to swift itself (we add a
'reveal_sensitive_prefix' configuration to the client).

With this patch, tokens are truncated by removing the specified number
of characters, after which '...' is appended to the logged token to
indicate that it has been redacted.

Also include client.parse_header_string() for safe unicode handling
of header data.

Backport based on commits:

  c3f06417049e17a8d45ee5926c5043cb6c8aa9ef
  4d44dcf36086add13d3353915c014f095ab99c6d
  ce569f46517e10f2ce0d27e9ee0a922ad1d84e2f
  46d817828082105a69d4da53fef2f2fbefc54809
  aa0edd00966237163451fc44cda2c593a5215cbe

Co-Authored-By: Tim Burke <tim.burke@gmail.com>
Co-Authored-By: Alistair Coles <alistair.coles@hpe.com>
Co-Authored-By: Li Cheng <shcli@cn.ibm.com>
Co-Authored-By: Zack M. Davis <zdavis@swiftstack.com>

Change-Id: I71fc5aad23bc076b06f75888c3ea507feffc7b48
Closes-bug: #1516692

Fix the http request headers in put_object being overwritten in logging

Cherry-picked from commit 61880c6f980cb8e613bdf6cb48a9a61ce7488162

Change-Id: Id0d1e36561a61ed1ce30d93c801ec32f058a6fa4
Closes-bug: #1501292

Needed for coverage 4.0

Change-Id: I2789541f67d6adbdc8454183753832488fe2bbe2
(cherry picked from commit ccc3aa49ee654286c169afce558455cfb9f2d4ba)

Change-Id: I2943b0dbcfc988bbd471b56ef7d02a515d49e16f

Instead of a 2.5.1 release, add in the absolute tempurl option to the release and bump it to 2.6.0

Change-Id: Ie8335a737aac3211a240c25d88501f8f5dbccbea

The `tempurl` subcommand's second positional argument is called
`seconds` and has heretofore interpreted as the number of seconds for
which the tempURL should be valid, counting from the moment of running
the command. This is indeed a common, if not the most common,
use-case. But some users, occasionally, might want to generate a tempURL
that expires at some particular ("absolute") time, rather than a
particular amount of time relative to the moment of happening to run the
command. (One might make an analogy to the way in which Swift's expiring
object support supports an `X-Delete-At` header in addition to
`X-Delete-After`—and it's the former that must be regarded as
ontologically prior.) Thus, this commit adds an `--absolute` optional
argument to the `tempurl` subcommand; if present, the `seconds` argument
will be interpreted as a Unix timestamp of when the tempURL should be
expire, rather than a duration for which the tempURL should be valid
starting from "now".

Change-Id: If9ded96f2799800958d5063127f3de812f50ef06

Change-Id: I1a264c9ce1d137b18a6dc62623a282e4a2fe839c