[NEXUS-5811] USe the absolute URL in RRB when the links are absolute and they do not start with proxy repository URL

https://issues.sonatype.org/browse/NEXUS-5811
https://bamboo.zion.sonatype.com/browse/NX-OSSF17

IN case that the index page returned from remote nexus has links that start with the forced base URL which are different then the proxy repository configured URL, use the absolute URLS returned by remote nexus.