Fix breaks against sysvinit (source package) to target sysvinit-core instead (binary package)
sysvinit is a source package, so the breaks to ensure a version with
the updated triggers is used are ineffective. Use the binary package
instead.
sysvinit used to be a binary package back in Jessie, so keep that breaks
too for extra safety.
Follow-up for e52e9835d934ee33d366707f54fc6674f19fd7df