install: create runtime data directory

install: create runtime data directory

On installation, make sure the data directory is created. This will
usually be /var/lib/suricata/data, but otherwise follows the
autoconf/automake instructions.

This directory is for runtime state information, which for now is
datasets but may be expanded in the future.  Suricata already expects
this directory to exist for "state" and "save" datasets, but it has
been up to the user to create it.