Ondrej Kozina authored Jun 07, 2016 and Milan Broz committed Jun 08, 2016

alter all checks for devfd value after device_open to
less than zero insted of equals to -1. device_open will
return values different from -1 in case error happens.

In LUKSv1 device_open should always return -1 in case of
error but this check is safer.

The rest is just formating improvement.