HADOOP-12559. KMS connection failures should trigger TGT renewal. Contributed by Zhe Zhang.

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

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/key/kms/KMSClientProvider.java

@@ -474,6 +474,8 @@ private HttpURLConnection createConnection(final URL url, String method)
           UserGroupInformation.AuthenticationMethod.PROXY)
                               ? currentUgi.getShortUserName() : null;
 
+      // check and renew TGT to handle potential expiration
+      actualUgi.checkTGTAndReloginFromKeytab();
       // creating the HTTP connection using the current UGI at constructor time
       conn = actualUgi.doAs(new PrivilegedExceptionAction<HttpURLConnection>() {
         @Override