Revert "HADOOP-19015. Increase fs.s3a.connection.maximum to 500 to minimize risk of Timeout waiting for connection from pool"

Pushed it by mistake. So sorry.
This reverts commit e28f83a1eb3eb0a9004d91fff18c238590da1d92.

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -1530,7 +1530,7 @@
 
 <property>
   <name>fs.s3a.connection.maximum</name>
-  <value>500</value>
+  <value>200</value>
   <description>Controls the maximum number of simultaneous connections to S3.
     This must be bigger than the value of fs.s3a.threads.max so as to stop
     threads being blocked waiting for new HTTPS connections.

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java

@@ -173,7 +173,7 @@ public final class Constants {
    * Future releases are likely to increase this value.
    * Keep in sync with the value in {@code core-default.xml}
    */
-  public static final int DEFAULT_MAXIMUM_CONNECTIONS = 500;
+  public static final int DEFAULT_MAXIMUM_CONNECTIONS = 200;
 
   /**
    * Configuration option to configure expiration time of