Atlas web UI inaccessible after adding Atlas service on upgraded cluster with Hive because /etc/atlas/conf symlink was created ahead of time

STR:

• Install Ambari 2.4.3 with HDP 2.5.3.0
• Include ZK, HDFS, MR, YARN, Hive (plus Pig, Tez, Slider), Kafka, Ambari Infra
• Install bits for HDP 2.5.5.0
• Perform EU
• Add Atlas as a service

There will be an alert for "Metadata Server Web UI" being inaccessible because /etc/atlas/conf/solr/ will contain the wrong configs after the upgrade.
This happens because installing Hive will also create artifacts in /usr/hdp/$version/atlas for the hooks, so when the bits are installed, it mistakenly creates /etc/atlas/conf as a broken symlink to /usr/hdp/current/atlas-client/conf (which doesn't exist yet). Because the symlink is broken to begin with, then adding Atlas for the first time does not populate the correct solr configs.

This is a regression of AMBARI-18368, now that /usr/hdp/current/atlas-client exists as a valid symlink even though Atlas is not actually installed.