librenms: workaround JunOS stupidness

Our librenms host is now dual-stacked (A & AAAA). JunOS (or at least the
version that we're running) is stupid, and treats a log target of "host
$hostname" with a dual stacked hostname as two log targets, multiplying
all log lines by two. Until a better fix is in place, bind rsyslog to
IPv4 only.

Change-Id: I4a911a3fad9c0d6c27796f7f2cd1bcba16e5eff8
librenms: make main class' "config" option simpler

Supplying install_dir, html_dir, rrd_dir & log file to the config hash
is kind of wrong, as it's not KISS: the class already knows the best
position for these and sets up other stuff based on these locations
(e.g. logrotate). Pass them to the config.php template instead, outside
of the config hash and simplify the caller.

Change-Id: I6620ff7bb206d8fee4fb18607930195382611ec9