Possible race conditions when re-staging changes that have just failed integration

This issue was seen by the error email "[Qt CI System Fatal Error] staging-approve failed" which was trying to perform

Command: ssh -p 29418 codereview.qt-project.org gerrit staging-approve -p qt/qtdeclarative.git -i master_201109301135 -r fail -m -

When reviewing the buildrefs for the previous and next to previous buildref it was seen the most recent changeids were a superset. The previous changeids were correctly flagged with INTEGRATING, however the next to previous were in some intermediate state and hence the failure of not being able to transition from a non INTEGRATING state.