hipos-device-info.sh: bug fixing and code review

The part of the code creating '/etc/hipos/hipos-device.<type>' (whose
existence is then used as a condition in systemd services) is now always
executed, even if we cannot access the board controller.

If no device type is set in the device file, 'unknown' is used. That is,
the file '/etc/hipos/hipos-device.unknown' will be created

Handling of several other errors has also been improved and made more
consistent.

Signed-off-by: Angelika Tobisch <tobisch@dresearch-fe.de>
Acked-by: Ralf Schröder <schroeder@dresearch-fe.de>
hipos-device-info.sh: make /etc/hydraip-devid the 'real' devid-file

Until now /etc/hipos/hipos-devid was the 'real' file, with the
legacy /etc/hydraip-devid as a symbolic link to it. This has now
been reversed. This change ensures the devid file survives updates
without any changes in the update procedure itself.

Signed-off-by: Angelika Tobisch <tobisch@dresearch-fe.de>
Acked-by: Ralf Schröder <schroeder@dresearch-fe.de>