Register service

COUCHDB-2796
diff --git a/src/couch_index_server.erl b/src/couch_index_server.erl
index 42a122b..0f18c0b 100644
--- a/src/couch_index_server.erl
+++ b/src/couch_index_server.erl
@@ -38,6 +38,7 @@
 -record(st, {root_dir}).
 
 start_link() ->
+    couch_epi:register_service(couch_index),
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).