Remove misleading exception "No running dag" from AM logs

15/01/14 16:45:06 INFO ipc.Server: IPC Server handler 0 on 51000, call org.apache.tez.dag.api.client.rpc.DAGClientAMProtocolBlockingPB.getDAGStatus from  Call#0 Retry#0
org.apache.tez.dag.api.TezException: No running dag at present
	at org.apache.tez.dag.api.client.DAGClientHandler.getDAG(DAGClientHandler.java:84)
	at org.apache.tez.dag.api.client.DAGClientHandler.getACLManager(DAGClientHandler.java:151)
	at org.apache.tez.dag.api.client.rpc.DAGClientAMProtocolBlockingPBServerImpl.getDAGStatus(DAGClientAMProtocolBlockingPBServerImpl.java:94)
	at org.apache.tez.dag.api.client.rpc.DAGClientAMProtocolRPC$DAGClientAMProtocol$2.callBlockingMethod(DAGClientAMProtocolRPC.java:7375)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:962)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2041)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2037)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:415)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2035)
15/01/14 16:45:06 INFO client.DAGClientImpl: DAG initialized: CurrentState=Running