add buildbot.util.asyncSleep
Add an integration test for try scheduler client/server interactions.

This runs a full master with real builds.

Waiting for SSH builds does not work - the buildmaster returns buildset
ID's, while the client expects its external_idstring, so it waits
forever.  This functionality will be difficult to support as-is in nine,
so it's been removed.
Merge remote-tracking branch 'origin/8/try-integration-test' (PR #1026)

+autopep8