Move HDFS-7546 to release 2.7.1 in CHANGES.txt.

(cherry picked from commit bcb3c40bed572a2dd95ce7201d893d7bf59240d5)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -316,9 +316,6 @@ Release 2.8.0 - UNRELEASED
     do not generate spurious reconfig warnings (Lei (Eddy) Xu via Colin P.
     McCabe)
 
-    HDFS-7546. Document, and set an accepting default for
-    dfs.namenode.kerberos.principal.pattern (Harsh J via aw)
-
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than
@@ -626,6 +623,9 @@ Release 2.7.1 - UNRELEASED
 
     HDFS-8361. Choose SSD over DISK in block placement.  (szetszwo)
 
+    HDFS-7546. Document, and set an accepting default for
+    dfs.namenode.kerberos.principal.pattern (Harsh J via aw)
+
   OPTIMIZATIONS
 
   BUG FIXES