ntp: Security fixes via Upgrade to 4.2.8p8

CVE-2016-4957
CVE-2016-4953
CVE-2016-4954
CVE-2016-4955
CVE-2016-4956

For more info to see:
http://support.ntp.org/bin/view/Main/SecurityNotice#June_2016_ntp_4_2_8p8_NTP_Securi



Signed-off-by: Fan Xin <fan.xin@jp.fujitsu.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>
(cherry picked from commit 13db3c65f525a6c87cd51961c3c1816e059478b9)
Signed-off-by: Armin Kuster <akuster808@gmail.com>