borg upgrade - fix locking
borg upgrade - fix locking

because Repository.__init__ normally opens and locks the repo, and the upgrader just
inherited from (borg) Repository, it created a lock file there before the "backup copy"
was made.

No big problem, but a bit unclean.

Fixed it to not lock at the beginning, then make the copy, then lock.

RonnyPfannschmidt/borg,RonnyPfannschmidt/borg,RonnyPfannschmidt/borg,edgimar/borg,raxenak/borg,edgewood/borg,mhubig/borg,edgimar/borg,edgewood/borg,RonnyPfannschmidt/borg,edgewood/borg,raxenak/borg,raxenak/borg,mhubig/borg,edgimar/borg,raxenak/borg,edgimar/borg,mhubig/borg,edgewood/borg,RonnyPfannschmidt/borg