Fix various features that didn't work /usr wasn't mounted in the initramfs.

Amongst other things, this commit drops the special-casing of /etc/localtime
when /usr is not part of the root fs, as timedated does not care about the
file content, only the symlink value.

To fix the real problem, that timezoned needs zoneinfo data which is located
in /usr, add RequiresMountsFor=usr/share/zoneinfo to the service file.
Add breaks on old syslog providers, they interact badly with the journal.
Add breaks on old resolvconf, it interacts badly with systemd-resolved.
Bump dependency on sysv-rc for an update-rc.d that works with systemd 214.
Rework support for Debian-specific locale, keyboard and timezone conf files.

This splits the existing patches into separate patches for each indepenent feature.
Rework the semantics of restart job deadlock avoidance during early boot and shutdown.
Replace one sysv-generator patch with the version I submitted upstream.
Rename one incredibly poorly named patch.