genconversion=false should skip fields during conversion generation

Currently it only skips if the fields don't match, but that leaves no
way for callers to say "no really, ignore this field".

cmd/libs/go2idl/conversion-gen/generators/conversion.go

@@ -352,16 +352,13 @@ func isDirectlyConvertible(in, out *types.Type, manualConversions conversionFunc
 	case types.Struct:
 		convertible := true
 		for _, inMember := range in.Members {
+			// Check if this member is excluded from conversion
+			if tagvals := extractTag(inMember.CommentLines); tagvals != nil && tagvals[0] == "false" {
+				continue
+			}
 			// Check if there is an out member with that name.
 			outMember, found := findMember(out, inMember.Name)
 			if !found {
-				// Check if the member has opted out with:
-				//   "+k8s:conversion-gen=false"
-				// TODO: Switch to SecondClosestCommentLines.
-				if tagvals := extractTag(inMember.CommentLines); tagvals != nil && tagvals[0] == "false" {
-					glog.V(5).Infof("field %v.%s requests no conversion generation, skipping", in, inMember.Name)
-					continue
-				}
 				return false
 			}
 			convertible = convertible && isConvertible(inMember.Type, outMember.Type, manualConversions)
@@ -727,6 +724,10 @@ func (g *genConversion) doSlice(inType, outType *types.Type, sw *generator.Snipp
 
 func (g *genConversion) doStruct(inType, outType *types.Type, sw *generator.SnippetWriter) {
 	for _, m := range inType.Members {
+		// Check if this member is excluded from conversion
+		if tagvals := extractTag(m.CommentLines); tagvals != nil && tagvals[0] == "false" {
+			continue
+		}
 		outMember, isOutMember := findMember(outType, m.Name)
 		if !isOutMember {
 			// Since this object wasn't filtered out, this means that