Perhaps better than changing apt-get's behavior is to hold oC packages for the time being
sudo apt-mark hold owncloud owncloud-files owncloud-deps-php7.0
You can always view held packages with sudo apt-mark showhold, and release them with sudo apt-mark unhold <package>.
Also of note is that the "Stable" PPA actually includes releases that are in advanced beta, and aren't considered suitable for production setting. Consider following only production-ready major releases, by changing your sources list. On Ubuntu, e.g., that's likely at /etc/apt/sources.list.d/owncloud.list, and you can change it from
deb http://download.owncloud.org/download/repositories/stable/<version>/
to, e.g.,
deb http://download.owncloud.org/download/repositories/9.1/<version>/