Fixed SCLScriptAnnotationModel script validation threading

Fixed SCLScriptAnnotationModel script validation threading

Previously the code performed the script validation directly in the DB
listener thread, which is essentially QueryThread-0 without putting the
related ReadGraph into the current SCLContext while doing so. This
caused the validation code to crash because the validation code tries to
start a new database transaction from within the transaction thread
calling the listener.

The solution schedules the validation to a BUILD priority Job thread.

refs #7450

Change-Id: I01c030be032890638919c3800e04e14670f8726c