The errors acbove occur when the installer finds an installation from an failed install attempt and tries to pdate it.
Please delete the installation and rerun the installer. If the installation fails you have to delete laways the install_ispconfig directory and the installation directorys:
rm -rf /home/admispconfig
rm -rf /root/ispconfig
And you will have to delete the ispconfig database or chose another database name for the next install atempt that is not in use on your server.