bind: Update ot 9.20.10

bind: Update ot 9.20.10

For details see:
https://downloads.isc.org/isc/bind9/9.20.10/doc/arm/html/notes.html#notes-for-bind-9-20-10

"Notes for BIND 9.20.10
New Features

    Implement a new notify-defer configuration option.
    This new option sets a delay (in seconds) to wait before sending a
    set of NOTIFY messages for a zone. Whenever a NOTIFY message is
    ready to be sent, sending is deferred for this duration. This
    option should not be confused with the notify-delay option. The
    default is 0 seconds. [GL #5259]

Removed Features

    Implement the systemd notification protocol manually to remove
    dependency on libsystemd.

Bug Fixes

    Fix zone deletion issue.
    A secondary zone could initiate a new zone transfer from the primary
    server after it had been already deleted from the secondary server,
    and before the internal garbage collection was activated to clean it
    up completely. This has been fixed. [GL #5291]

    Fix a zone refresh bug.

    A secondary zone could fail to further refresh with new versions of
    the zone from a primary server if named was reconfigured during the
    SOA request step of an ongoing zone transfer. This has been fixed.
    [GL #5307]"

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Reviewed-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>