Reenable percolator

Relates elastic#24317
Relates elastic/rally-tracks#26

Author: danielmitterdorfer

night_rally.py

@@ -25,10 +25,9 @@
     ["append-no-conflicts-index-only", "verbose_iw"]
 ]
 
-# temporarily disabled due to https://github.com/elastic/elasticsearch/pull/24317
-# tracks["percolator"] = [
-#     ["append-no-conflicts", "4gheap"]
-# ]
+tracks["percolator"] = [
+    ["append-no-conflicts", "4gheap"]
+]
 
 tracks["geopoint"] = [
     ["append-no-conflicts", "defaults"],