Factor out buildset addition testing

Only test schedulers' calls to the BaseScheduler addBuildsetForXxx
methods.
Merge branch '9/buildset-rtype' into nine
Merge branch 'nine' of github.com:buildbot/buildbot into nine
remove comment that is ultimately meaningless
Merge branch '9/masters-table' into nine
fix compatibility with sqlalchemy<0.7.0
Only send messages about deactivated masters if they're actually deactivated

As pointed out by tomprince
add comment about BuildMaster calling db.masters.findMasterId
factor master expiry into a new update method

as suggested by tomprince
addBuildset takes a scheduler *name*, not object

The wrong behavior was being enforced by the tests!
addBuidlset takes a scheduler name, not object - fix the real implementation too
restore master.addBuildset, with deprecation warning
factor findXxxId methods into a base method
do not look at inherited class attributes for endpoint settings
Merge branch 'master' into nine

Conflicts:
	master/docs/manual/cfg-global.rst
Merge branch '9/endpoint-class-attrs' of git://github.com/djmitche/buildbot into nine
WIP: Adding UserCancel to list of available status. (ref: Moz bmo: bug
fix tests to use the masters table (which exists) rather than schedulers (which doesn't)
use fetchone, as it's more explicit
- Updated docs and comment.