fix for GRAILS-11227 "running unit test in interactive mode, the first time is ok while the second time it fails."
fix for GRAILS-10920 "Config gets executed multiple times"
fix failing test
Improve previous fix, only load from holders if explicitly told to in dev environment
Merge branch '2.3.x'

Conflicts:
	grails-core/src/main/groovy/org/codehaus/groovy/grails/commons/cfg/ConfigurationHelper.groovy