YARN-6786. [YARN-3926] ResourcePBImpl imports cleanup. Contributed by Yeliang Cang.

(cherry picked from commit 4e5632d28eb8f6b1b8830c2aa89ec6321d477977)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/api/records/impl/pb/ResourcePBImpl.java

@@ -18,7 +18,6 @@
 
 package org.apache.hadoop.yarn.api.records.impl.pb;
 
-import org.apache.commons.collections.map.UnmodifiableMap;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience.Private;
@@ -34,7 +33,10 @@ import org.apache.hadoop.yarn.proto.YarnProtos.ResourceInformationProto;
 import org.apache.hadoop.yarn.util.resource.ResourceUtils;
 import org.apache.hadoop.yarn.util.UnitsConversionUtil;
 
-import java.util.*;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Collections;
+
 
 @Private
 @Unstable