I got the problem that the Server Manager installs the Beta branch of Avorion (0.16.7.11165), but while the installation of DSM i have selected to install the stable branch.
To check if it was my failure, i installed another linux machine from ground up and the DSM too, but on this brand new machine too, it installs the Beta-server.
EDIT:
If i install the avorion-server from hand, without DSM, it chooses the stable branch. So it's a problem with the DSM, not with steamcmd.