Executive summary: during yum update, don't try to move ~hudson to ~jenkins if the two paths are the same!

Details ...

I ran "yum install jenkins" to switch our installation from hudson to jenkins. I can't remember where the old data lived when I did this, because I rebuilt the server at the same time; my memory is that I put it in ~hudson, but copied it by hand to ~jenkins after the install because the install didn't copy it even though ~jenkins/.moving-hudson was created. At some point (afterwards?) I modified the password entry for hudson to have the same home directory as jenkins, so that ~hudson in scripts would still work.

Today I did "yum update", and it tried to move ~hudson to ~jenkins (mv complained that the files were the same, of course), and then it tried to delete ~hudson which was the same as ~jenkins?! Luckily, ~jenkins was a file system mount point, so the delete failed.