Updating CHANGES.txt for TEZ-2575 and TEZ-2602 backports to branch-0.7 (rbalamohan)
Updating CHANGES.txt for TEZ-2575 and TEZ-2602 backports to branch-0.7 (rbalamohan)

Parth-Brahmbhatt/tez,sidseth/tez,sidseth/tez,jth/tez,sidseth/tez,guiling/tez,dongjiaqiang/tez,ueshin/apache-tez,ChetnaChaudhari/tez,apache/tez,Parth-Brahmbhatt/tez,guiling/tez,dongjiaqiang/tez,jth/tez,sidseth/tez,jth/tez,Parth-Brahmbhatt/tez,dongjiaqiang/tez,apache/tez,apache/tez,ChetnaChaudhari/tez,guiling/tez,guiling/tez,apache/tez,ueshin/apache-tez,Parth-Brahmbhatt/tez,ueshin/apache-tez,dongjiaqiang/tez,ChetnaChaudhari/tez,jth/tez,dongjiaqiang/tez,Parth-Brahmbhatt/tez,ueshin/apache-tez,ueshin/apache-tez,guiling/tez,jth/tez,sidseth/tez,apache/tez,ChetnaChaudhari/tez,ChetnaChaudhari/tez