Was running coredns-master on my servers and kept seeing:

~~~
okt 14 10:38:06.473281 deb coredns[30303]: [INFO] plugin/transfer: Outgoing incremental transfer for up to date zone "miek.nl." to 37.97.149.87 for 1602370680 SOA serial
okt 14 10:40:06.498512 deb coredns[30303]: [INFO] plugin/transfer: Outgoing incremental transfer for up to date zone "miek.nl." to 37.97.149.87 for 1602370680 SOA serial
okt 14 10:42:06.553747 deb coredns[30303]: [INFO] plugin/transfer: Outgoing incremental transfer for up to date zone "miek.nl." to 37.97.149.87 for 1602370680 SOA serial
~~~

and I'm like shouldn't that be noop transfer? And sure enough, a
duplicated code block in the transfer code that logs this, so the `noop`
line is never reached.
Signed-off-by: Miek Gieben <miek@miek.nl>