Fix the search request default operation behavior doc (#29302) (#29405)

Ke Li · colings86 · commit 3cc1a52caa57 · 2018-05-08T17:47:01.000+01:00
diff --git a/docs/reference/search/request/preference.asciidoc b/docs/reference/search/request/preference.asciidoc
@@ -2,7 +2,8 @@
 === Preference
 
 Controls a `preference` of which shard copies on which to execute the
-search. By default, the operation is randomized among the available shard copies.
+search. By default, the operation is randomized among the available shard 
+copies, unless allocation awareness is used.
 
 The `preference` is a query string parameter which can be set to:
 
