ipa-backup: fix python2 issue with os.mkdir
Python2 and python3 have different interfaces for os.mkdir:
python2: os.mkdir(path[, mode])
python3: os.mkdir(path, mode=0o777, *, dir_fd=None)
ipa-backup is using the python3 format, which breaks deployments using
python2. The fix consists in using os.mkdir(path, 0o700) instead of
os.mkdir(path, mode=0o700).
Fixes: https://pagure.io/freeipa/issue/8099
Reviewed-By: Alexander Bokovoy <abbra@users.noreply.github.com>