Add whitelist entry for s-proxy 'Timeout talking to memcached'

According to John Dickinson:

"This isn't an error. It's logged at an error level because it may hint
at other problems, and it's something an operator needs to know about,
but it is not an unhandled failure condition. (Think of it similarly how
in swift a server being down is an "error", but it's something that
swift seamlessly works around.)"

Closes-Bug: #1260894

Change-Id: I41e55c5e34ee214727fbbd7b9daa1f6ea9bf8050
Set pipefail for wrapper scripts

Previously if the testr list command was failing subunit2py would
return a 0 making the test runs that use the pretty_tox scripts also
return 0 despite testr actually failing. This commit gets around this
condition by setting pipefail in the pretty_tox scripts to ensure that
we actually fail.

Change-Id: I9cbaf83cfea7c02133b27fe639e7ea12edb48f7e
Merge "Set pipefail for wrapper scripts"
Merge "Add whitelist entry for s-proxy 'Timeout talking to memcached'"