Reduce pathfinding times when large underspecified STP are provided.

[jmacauley]

When a pathfinding request is received with a large range of underspecified STP it can take an extremely long time to determine the optimal shortest path causing clients to timeout. A more responsive solution should be provided.

The following is an example of an extremely large underspecified range resulting in roughly 2,954,081,820 path combinations:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns4:local xmlns:ns2="http://schemas.es.net/nsi/2013/08/pce/messages" xmlns:ns4="uri" xmlns:ns3="http://schemas.ogf.org/nsi/2013/12/services/point2point">
    <correlationId>urn:uuid:682ff91d-96ab-4248-96b8-bb7c1f3c6663</correlationId>
    <replyTo>
        <url>https://agg.netherlight.net/pce/reply</url>
        <mediaType>application/json</mediaType>
    </replyTo>
    <algorithm>TREE</algorithm>
    <startTime>2016-08-22T16:03:00.000+02:00</startTime>
    <endTime>2016-08-22T18:03:00.000+02:00</endTime>
    <serviceType>http://services.ogf.org/nsi/2013/12/descriptions/EVTS.A-GOLE</serviceType>
    <trace index="0">urn:ogf:network:surfnet.nl:1990:nsa:nsi-requester:noId</trace>
    <ns3:p2ps>
        <capacity>103</capacity>
        <directionality>Bidirectional</directionality>
        <symmetricPath>true</symmetricPath>
        <sourceSTP>urn:ogf:network:netherlight.net:2013:production7:microsoft-2?vlan=2-4095</sourceSTP>
        <destSTP>urn:ogf:network:geant.net:2013:topology:JANET__eMusic__Edinburgh__port?vlan=2-2094</destSTP>
        <ero>
            <orderedSTP order="0">
                <stp>urn:ogf:network:netherlight.net:2013:production7:geant-3?vlan=3750-4095</stp>
            </orderedSTP>
        </ero>
        <parameter type="protection">PROTECTED</parameter>
    </ns3:p2ps>
</ns4:local>