Fixing electron selection pre-selection flags

This is a small change which fills the electron pre-selection flags, passMvaPreslection_ and passPflowPreselection_ which were currently not being filled. 

If this is a problem for 73X, it can go for 74X, its just the flags wont be filled. The information is slightly redundant but as they are there, it is our view we might as well fill them. 

It is related to https://github.com/cms-sw/cmssw/pull/6479.  I decided not to add back in the error message is its still possible that this error condition can happen if we changed the python config and its not technically an error.