Parameterize the random device for dnssec-keygen

`dnssec-keygen` uses `/dev/random` by default, but this is slow in some
scenarios where `/dev/urandom` is both faster and provides sufficient utility.
Allow override via the `bind::random_device` hiera key.

manifests/init.pp

@@ -2,13 +2,14 @@
 
 class bind (
     $confdir         = undef,
-    $namedconf        = undef,
+    $namedconf       = undef,
     $cachedir        = undef,
     $forwarders      = undef,
     $dnssec          = undef,
     $version         = undef,
     $rndc            = undef,
     $statistics_port = undef,
+    $random_device   = undef,
 ) {
     include ::bind::params
 

manifests/zone.pp

@@ -21,6 +21,7 @@ define bind::zone (
     # where there is a zone, there is a server
     include bind
     $cachedir = $::bind::cachedir
+    $random_device = $::bind::random_device
     $_domain = pick($domain, $name)
 
     unless !($masters != '' and ! member(['slave', 'stub'], $zone_type)) {
@@ -109,7 +110,7 @@ define bind::zone (
     if $dnssec {
         exec { "dnssec-keygen-${name}":
             command => "/usr/local/bin/dnssec-init '${cachedir}' '${name}'\
-                '${_domain}' '${key_directory}'",
+                '${_domain}' '${key_directory}' '${random_device}'",
             cwd     => $cachedir,
             user    => $::bind::params::bind_user,
             creates => "${cachedir}/${name}/${_domain}.signed",