DNS import mishandled bind zone file syntax

When importing a DNS bind9 zone file, records are not handled correctly if they do not include the optional hostname.

Eg. this is valid syntax, which we use widely (eg. when named writes a zone in text format):

host123  A   1.2.3.4
         MX  host123
         TXT "v=spf1 a -all"

Instead of 3 records (A, MX, TXT) for 'host123' being created, this turns into an A record for 'host123' and 2 records (MX, TXT) for hostname 'in'.

This includes records for the domain itself, eg. we often use something like:

$ORIGIN domain.tld.
$TTL 3600

@               IN      SOA     ns1.domain.tld. hostmaster.domain.tld. (
                                2020032601 ; Serial
                                7200    ; Refresh, seconds
                                540     ; Retry, seconds
                                604800  ; Expire, seconds
                                3600 )  ; Minimum, seconds

                IN      A       1.2.3.4

                IN      NS      ns1.domain.tld.
                IN      NS      ns2.domain.tld.

                IN      MX      10 mx1.domain.tld.
                IN      MX      20 mx2.domain.tld.

                IN      TXT     "v=spf1 a mx ~all"