Set the release date for 2.5.2

(cherry picked from commit 68a050872896f93582f95420dd6e2bdefa4fd7cc)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
HADOOP-11296. Nfs3FileAttributes should not change the values of rdev, nlink and size in the constructor. Contributed by Brandon Li.
HADOOP-9576. Changed NetUtils#wrapException to throw EOFException instead of wrapping it as IOException. Contributed by Steve Loughran
(cherry picked from commit 86bf8c7193013834f67e03bd67a320cc080ef32c)
YARN-2841. RMProxy should retry EOFException.  Contributed by Jian He

(cherry picked from commit 5c9a51f140ba76ddb25580aeb288db25e3f9653f)
YARN-2841: Correct fix version from branch-2.6 to branch-2.7 in the
change log.

(cherry picked from commit 58e9bf4b908e0b21309006eba49899b092f38071)