debian: add a hard dependency on logsave to e2fsprogs
The initramfs created by the initramfs-tools package needs logsave and
assumes it comes along with e2fsprogs. If it is not present, the
result systems which will fail to boot. Fix this by adding the
dependency.
In the future initramfs-tools will explicitly ask for logsave (tracked
in Debian Bug: #932854), but we'll need to keep this dependency until
the next stable release of Debian.