Add filetrans for ntp-kod file

sntp has a file used to persist the history of KoD responses
received from servers.  The  default  is /var/db/ntp-kod.

This patch adds the fcontext and a filetrans so it can be created.

Changes from v1:
* use files_var_filetrans instead of filetrans_pattern

Signed-off-by: Jason Zaman <jason@perfinion.com>
Remove name from ntp-kod ntp_drift_t filetrans.
Module version bump for ntp-kod file support from Jason Zaman.