linux/if_err: suggest interfaces not ending in a digit

See Ticket #943 and r4690 for the same change in if_.

plugins/node.d.linux/if_err_.in

@@ -61,11 +61,7 @@ fi
 
 if [ "$1" = "suggest" ]; then
     if [ -r /proc/net/dev ]; then
-	awk '
-            /^ *(eth|tap|bond|wlan|ath|ra|sw|vlan|venet|veth|msh)[0-9]+(\.[0-9]+)?:/ {
-                 split($0, a, /: */);
-                 gsub(/^ +/,"",a[1]);
-                 if (($2 > 0) || ($10 > 0)) print a[1]; }' /proc/net/dev
+        sed -rne '/^[[:space:]]*(lo|sit[[:digit:]]+):/d;s,^[[:space:]]*([^:]+):.*,\1,p' /proc/net/dev
     fi
     exit 0
 fi