[citrain] Overlay PPA is pinned down and packages can't be installed

Today, we couldn't install a system-settings silo using citrain, because it kept back the package. The silo package required a dependency available in the overlay PPA, and the overlay PPA is currently pinned down to 50. citrain line:

loudly "echo -e 'Package: *\nPin: release o=*$SILO*\nPin-Priority: 1100\n\nPackage: *\nPin: release a=$SERIES*\nPin-Priority: 50' | SUDO_ASKPASS=/tmp/askpass.sh sudo -A tee /etc/apt/preferences.d/extra-ppas.pref"

Please, pin up the overlay PPA back to 1000.