Made sure to instrument the old mapper as well as the new mapper
Add XTrace as a Maven dependency.

Conflicts:
	hadoop-common-project/hadoop-common/pom.xml
Instrumentation of RPC layer
Conflicts:

	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java

Conflicts:

	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetUtils.java

Conflicts:
	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java
	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java
	hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ProtoUtil.java
	hadoop-common-project/hadoop-common/src/main/proto/RpcPayloadHeader.proto