wrong solr ping URL

[rocket-turtle]

With c4ee8e0 the Ping URL changed from /admin/ping back to /ping

[2] pry(SunspotTest)> Net::HTTP.get_response(URI.parse("#{Sunspot.session.config.solr.url}/admin/ping"))
=> #<Net::HTTPOK 200 OK readbody=true>
[3] pry(SunspotTest)> Net::HTTP.get_response(URI.parse("#{Sunspot.session.config.solr.url}/ping"))
=> #<Net::HTTPNotFound 404 Not Found readbody=true>

They both somehow work put /admin/ping is the correct ping URL and is also used by sunspot

https://github.com/sunspot/sunspot/blob/master/ci/travis.sh#L9

solr_responding() {
  port=$1
  curl -o /dev/null "http://localhost:$port/solr/admin/ping" > /dev/null 2>&1
}

https://lucene.apache.org/solr/4_2_0/solr-core/org/apache/solr/handler/PingRequestHandler.html