rc.d/random: bring back rc.conf defaults, minor fixes
* Saving the entropy across reboots is good practice to
avoid having a lack of entropy after restarting the
machine. For some reason, it has been disabled by default
for ages now.
* This commit brings back the defaults in rc.conf to enable
saving entropy across reboots.
* Minor fixes to rc.d/random, such as not assuming
/var/db/entropy is a good place to put the entropy file,
last but not least because:
- that location is not checked on the start part of the script,
so it won't ever be used.
- /var/db/entropy is most of the time a directory, for the
cron-based entropy collection.