implement ignore_layers, force_macsuck, force_arpnip config settings (#1002)

* implementation of ignore_layers, force_macsuck, force_arpnip and macwalk

* use new WalkJobs view to get devices needing macsuck

* also new query for discoverall, arpwalk, nbtwalk

* faux record has a last_defer stamp so we can see when the backend started

* fix typo

lib/App/Netdisco/DB/Result/Virtual/WalkJobs.pm

@@ -0,0 +1,43 @@
+package App::Netdisco::DB::Result::Virtual::WalkJobs;
+
+use strict;
+use warnings;
+
+use base 'DBIx::Class::Core';
+
+__PACKAGE__->table_class('DBIx::Class::ResultSource::View');
+
+__PACKAGE__->table('walk_jobs');
+__PACKAGE__->result_source_instance->is_virtual(1);
+__PACKAGE__->result_source_instance->view_definition(<<ENDSQL
+    SELECT ip
+    FROM device
+
+    LEFT OUTER JOIN admin ON (device.ip = admin.device
+                              AND admin.status = 'queued'
+                              AND admin.action = ?)
+
+    FULL OUTER JOIN device_skip ON (device_skip.device = device.ip
+                                    AND (device_skip.actionset @> string_to_array(?, '')
+                                         OR (device_skip.deferrals >= ?
+                                             AND device_skip.last_defer > (LOCALTIMESTAMP - ? ::interval))))
+
+    WHERE admin.device IS NULL
+      AND device.ip IS NOT NULL
+      AND (device.vendor IS NULL OR device.vendor != 'netdisco')
+
+    GROUP BY device.ip
+    HAVING count(device_skip.backend) < (SELECT count(distinct(backend)) FROM device_skip)
+
+    ORDER BY device.ip ASC
+ENDSQL
+);
+
+__PACKAGE__->add_columns(
+  "ip",
+  { data_type => "inet", is_nullable => 0 },
+);
+
+__PACKAGE__->set_primary_key("ip");
+
+1;