sbackupd lock file generation is not atomic

[Helmut Raiger]

Binary package hint: sbackup

The lock file generation in sbackupd.py is not atomic as it tries to open the lockfile for read and if this fails it creates it by opening it for write.

Something like:

try:
            fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR)
except OSError, e:
            if e.errno != errno.EEXIST:

should fix the issue.