ntp: multiple issues

Keys explicitly generated by "ntp-keygen -M" should be regenerated.

• CVE-2014-9293 (weak key generation)
  ntpd generated a weak key for its internal use, with full administrative
  privileges. Attackers could use this key to reconfigure ntpd (or to
  exploit other vulnerabilities).

• CVE-2014-9294 (weak key generation)
  The ntp-keygen utility generated weak MD5 keys with insufficient
  entropy, which makes it easier for remote attackers to defeat
  cryptographic protection mechanisms via a brute-force attack.

• CVE-2014-9295 (arbitrary code execution)
  Multiple stack-based buffer overflows in allow remote attackers to
  execute arbitrary code via a crafted packet, related to (1) the
  crypto_recv function when the Autokey Authentication feature is used,
  (2) the ctl_putdata function, and (3) the configure function.

• CVE-2014-9296 (unintended association change)
  The receive function in ntp_proto.c continues to execute after detecting
  a certain authentication error, which might allow remote attackers to
  trigger an unintended association change via crafted packets.