Handle differences in how po_with_problems works in the olden times

In this version of yum, the second package in the tuple can sometimes be None.
Modify the sequence returned by enumerate instead of setting a start

"Changed in version 2.6: The start parameter was added."
Fix the handling of some rpm calls.

In the time of the dinosaurs, hdrFromFdno only accepted ints and did not
understand file-like objects, and the addInstall upgrade flag had to be a
letter for some reason.
Don't pass self to the rpmts pseudo-parent.

Oops.