Merge pull request #4532 from edx/pwnage101/bump-num-executors-jenkins-build-docker

bump the number of executors on the jenkins build docker image

docker/build/jenkins_build/ansible_overrides.yml

@@ -45,3 +45,8 @@ jenkins_common_main_labels:
   - 'dsl-seed-runner'
   - 'backup-runner'
   - 'jenkins-worker'  # added this
+
+# We're running all our jobs on the Jenkins Master by default (one container
+# only), so we need to bump up the number of executors for some jobs with
+# downstream jobs to work correctly.
+jenkins_common_main_num_executors: 6