Don't overwrite RETRY status when handling interrupts.
Merge branch 'dont-override-retry' of git://github.com/bhearsum/buildbot
ignore http proxy env variables during http step tests

When running unit tests of buildbot.steps.http, ignore http
proxy environment variables. Otherwise tests will try to make
http requests via proxy if for example 'http_proxy' variable
is set.
Merge branch 'http-step-proxy' of git://github.com/elmirjagudin/buildbot