Simplify Layer3::OneAccess model method since it is returning a static string

Add Layer3::OneAccess test class and POD updates

lib/SNMP/Info/Layer3/OneAccess.pm

@@ -64,13 +64,8 @@ sub vendor {
 }
 
 sub model {
-  my $OneAccess = shift;
-  my $descr = $OneAccess->description() || '';
-  my $model = undef;
+  return 'One300';
 
-  $model = 'One300';
-
-  return $model;
 }
 
 sub os {
@@ -143,6 +138,10 @@ Subclass for OneAccess Quidway switches
 
 =back
 
+=head2 Required MIBs
+
+=over
+
 =item Inherited Classes' MIBs
 
 See L<SNMP::Info::Layer3> for its own MIB requirements.