Major Description
I was working with Noble Paul to investigate test failures seen in SOLR-12806 where we found this issue. Due to a bug, replicas of a collection weren't spread evenly so there were some nodes which did not have any replicas at all. In such cases, when a v2 API call hits an empty node, it is not forwarded to the right path on the remote node causing test failures.
e.g. a call to /c/collection/_introspect is forwarded as http://127.0.0.1:63326/solr/collection1/_introspect?method=POST&wt=javabin&version=2&command=XXXX and /c/collection1/abccdef is forwarded as http://127.0.0.1:63326/solr/collection1/abccdef
In summary, a remote query for v2 API from an empty node is converted to a v1 style call which may not be a valid path. We should forward v2 API calls as-is without changing the paths.