ntpd: daemonize before DNS resolution

ntpd: daemonize before DNS resolution

This resolves the following use case problem:

"I start ntpd by default from /etc/init.d

There might be no working network connection (not configured properly for
whatever reason, hardware problems, whatelse).

With busybox 1.25 ntpd seems to loop forever if now NTP servers are found,
blocking the boot process  and I never get a login to solve a possible pb or
to do a first time configuration."

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>