tests/dnsd: read config from file

Make the <dns> tag in a test case control what is stored there. Also
documented. Make test 2102 and 2103 use the new tag.

Lets the test case config the A and AAAA contents the server replies
with. Initial work for the HTTPS RR exists, but does not yet work.

Closes #17543

tests/data/Makefile.am

@@ -253,7 +253,7 @@ test2064 test2065 test2066 test2067 test2068 test2069 test2070 test2071 \
 test2072 test2073 test2074 test2075 test2076 test2077 test2078 test2079 \
 test2080 test2081 test2082 test2083 test2084 test2085 test2086 test2087 \
 test2088 test2089 \
-test2100 test2101 test2102 \
+test2100 test2101 test2102 test2103 \
 \
 test2200 test2201 test2202 test2203 test2204 test2205 \
 \

tests/data/test2102

@@ -23,6 +23,10 @@ Funny-head: yesyes
 
 -foo-
 </data>
+<dns>
+A: %HOSTIP
+AAAA: %HOST6IP
+</dns>
 </reply>
 
 #

tests/data/test2103

@@ -0,0 +1,45 @@
+<testcase>
+<info>
+<keywords>
+DNS fail
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<dns>
+A: none
+AAAA: none
+</dns>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+dns
+</server>
+<features>
+override-dns
+</features>
+<name>
+HTTP GET with bad host name
+</name>
+<setenv>
+CURL_DNS_SERVER=127.0.0.1:%DNSPORT
+</setenv>
+<command>
+http://examplehost.example/%TESTNUMBER
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+# curl: (6) Could not resolve host: examplehost.example
+<errorcode>
+6
+</errorcode>
+</verify>
+</testcase>