Remove extraneous log message

When ntp switched between PLL and FLL mode it produced a log message
"kernel time sync status change %04x". This issue is reported in ntp
bug 452[1] which claims that this behaviour is normal and the log
message isn't necessary. I'm not sure exactly when it was removed, but
it's gone in the latest ntp release (4.2.6p5).

[1] http://bugs.ntp.org/show_bug.cgi?id=452

Approved by: roberto