file-posix: Fix creation locking

raw_apply_lock_bytes() takes a bit mask of "permissions that are NOT
shared".

Also, make the "perm" and "shared" variables uint64_t, because I do not
particularly like using ~ on signed integers (and other permission masks
are usually uint64_t, too).

Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>