Updated ntp packages fix security vulnerability

A vulnerability was found in NTP, in the legacy MX4200 refclock implementation. If this refclock was compiled in and used, an attacker may be able to induce stack overflow, leading to a crash or potential code execution (CVE-2017-6451). A vulnerability was found in NTP, in the building of response packets with custom fields. If custom fields were configured in ntp.conf with particularly long names, inclusion of these fields in the response packet could cause a buffer overflow, leading to a crash (CVE-2017-6458). A vulnerability was found in NTP, in the parsing of packets from the /dev/datum device. A malicious device could send crafted messages, causing ntpd to crash (CVE-2017-6462). A vulnerability was discovered in the NTP server’s parsing of configuration directives. A remote, authenticated attacker could cause ntpd to crash by sending a crafted message (CVE-2017-6463). A vulnerability was discovered in the NTP server’s parsing of configuration directives. A remote, authenticated attacker could cause ntpd to crash by sending a crafted message (CVE-2017-6464).