CHANGES.txt: add HADOOP-11257

(cherry picked from commit c1f2bb2d31d40bda5bb2c5bdf31e4f6e433d1e77)
HADOOP-11341. KMS support for whitelist key ACLs. Contributed by Arun Suresh.

(cherry picked from commit 31b4d2daa14a7f6e8ee73fd3160e126d8db62ffb)