remove die() calls

lib/App/Netdisco/Worker/Plugin/Arpnip/Subnets.pm

@@ -34,7 +34,7 @@ sub gather_subnets {
   my @subnets = ();
 
   my $snmp = App::Netdisco::Transport::SNMP->reader_for($device)
-    or die "arpnip failed: could not SNMP connect to $device";
+    or return (); # already checked!
 
   my $ip_netmask = $snmp->ip_netmask;
   foreach my $entry (keys %$ip_netmask) {

lib/App/Netdisco/Worker/Plugin/Discover/Neighbors.pm

@@ -86,7 +86,7 @@ sub store_neighbors {
   my @to_discover = ();
 
   my $snmp = App::Netdisco::Transport::SNMP->reader_for($device)
-    or die "discover failed: could not SNMP connect to $device";
+    or return (); # already checked!
 
   # first allow any manually configured topology to be set
   set_manual_topology($device);
@@ -287,9 +287,7 @@ sub store_neighbors {
 # in the devices table. only use root_ips and skip any bad topo entries.
 sub set_manual_topology {
   my $device = shift;
-
-  my $snmp = App::Netdisco::Transport::SNMP->reader_for($device)
-    or die "discover failed: could not SNMP connect to $device";
+  my $snmp = App::Netdisco::Transport::SNMP->reader_for($device) or return;
 
   schema('netdisco')->txn_do(sub {
     # clear manual topology flags

lib/App/Netdisco/Worker/Plugin/Macsuck/Nodes.pm

@@ -152,7 +152,7 @@ sub get_vlan_list {
   my $device = shift;
 
   my $snmp = App::Netdisco::Transport::SNMP->reader_for($device)
-    or die "macsuck failed: could not SNMP connect to $device";
+    or return (); # already checked!
 
   return () unless $snmp->cisco_comm_indexing;
 
@@ -269,7 +269,7 @@ sub walk_fwtable {
   my $cache = {};
 
   my $snmp = App::Netdisco::Transport::SNMP->reader_for($device)
-    or die "macsuck failed: could not SNMP connect to $device";
+    or return $cache; # already checked!
 
   my $fw_mac   = $snmp->fw_mac;
   my $fw_port  = $snmp->fw_port;