Add support for submitting build request to Buildbot 0.9 server in BuildbotSyncer

Add support for submitting build request to Buildbot 0.9 server in BuildbotSyncer
https://bugs.webkit.org/show_bug.cgi?id=182218

Reviewed by Ryosuke Niwa.

* tools/js/buildbot-syncer.js:
(BuildbotSyncer.prototype.scheduleRequest): Added assert to ensure forcescheduler property is always defined. Builds can not
be scheduled on Buildbot without this property. Updated unit-tests and server-tests accordingly.
(BuildbotSyncer.prototype.scheduleBuildOnBuildbotDeprecated): Method to schedule build request on Buildbot 0.8 server.
(BuildbotSyncer.prototype.scheduleBuildOnBuildbot): Method to schedule build request on Buildbot 0.9 server.
(BuildbotSyncer.prototype.pathForForceBuildDeprecated): Path for scheudling build on Buildbot 0.8 server.
(BuildbotSyncer.prototype.pathForForceBuild): Path for scheudling build on Buildbot 0.9 server.
* unit-tests/buildbot-syncer-tests.js:
(smallConfiguration): Added test-case for scheduleBuildOnBuildbot. Also added forcescheduler property in sample data.
* server-tests/resources/mock-data.js: Added forcescheduler property in sample data.
* server-tests/tools-buildbot-triggerable-tests.js: Updated server-tests to take care of added forcescheduler property.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@228099 268f45cc-cd09-0410-ab3c-d52691b4dbfc