do not flush the session anymore

[zyro23]

for some time now, the quartz plugin already takes care of flushing the session after a job was executed properly using the HibernatePersistenceContextInterceptor. and does that in a hibernate-5.2 safe way. https://github.com/grails-plugins/grails-quartz/blob/v2.0.12/src/main/groovy/grails/plugins/quartz/listeners/SessionBinderJobListener.java#L81

quartz-monitor plugin should not attempt to flush the session as that can lead to a TransactionRequiredException with hibernate-5.2.

ref. grails/grails-data-mapping#898

will send a pr.

thanks, zyro