DNS resolution is broken for some addresses in master/2.0-pre

[pfalcon]

Steps to reproduce: Apply following patch:

diff --git a/samples/net/sockets/http_get/src/http_get.c b/samples/net/sockets/http_get/src/http_get.c
index 4c2ebd2962..016014e45c 100644
--- a/samples/net/sockets/http_get/src/http_get.c
+++ b/samples/net/sockets/http_get/src/http_get.c
@@ -28,7 +28,7 @@
 #endif
 
 /* HTTP server to connect to */
-#define HTTP_HOST "google.com"
+#define HTTP_HOST "mqtt.2030.ltsapis.goog"
 /* Port to connect to, as string */
 #if defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS)
 #define HTTP_PORT "443"

And run the sample above. In other words, try to resolve address "mqtt.2030.ltsapis.goog" (this is valid address, used by Google's https://github.com/GoogleCloudPlatform/iot-device-sdk-embedded-c)

The culprit, from bisecting, is ef10937:

ef1093755328e7ecab2965b273110d57b4d76931 is the first bad commit
commit ef1093755328e7ecab2965b273110d57b4d76931
Author: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Date:   Tue Jun 25 10:01:54 2019 +0300

    net: dns: Make dns_unpack_answer() to check non-compressed answers
    
    Modify dns_unpack_answer() function to check if the answer is
    compressed or not, and return correct values regardless.
    
    Fixes #16594
    
    Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>

[pfalcon]

Specific output from that sample is:

Booting from ROM..***** Booting Zephyr OS build zephyr-v1.14.0-1931-gef1093755328 *****
[00:00:00.010,000] <inf> net_config: Initializing network
[00:00:00.010,000] <inf> net_config: IPv4 address: 192.0.2.1
Preparing HTTP GET request for http://mqtt.2030.ltsapis.goog:80/
getaddrinfo status: -4
Unable to resolve address, quitting

The expected output is getaddrinfo status: 0.

[pfalcon]

Ok, confirmed that git revert ef1093755328e7ecab2965b273110d57b4d76931 succeeds and fixes this issue.

[pfalcon]

Analysis of ef10937, which introduced regression: ef10937#r34743268

Summary: this processing needs to be rewritten from scratch.