[autotest-client-tests][PATCH] UBUNTU: SAUCE: ubuntu_fan_smoke_test: use resolvectl for parsing DNS server by default

[Po-Hsu Lin]

Some SUT will have more than one DNS server, example below is the
output from node spitfire with Focal in Intel MAAS:
    Current DNS Server: 8.8.8.8
    DNS Servers: 192.168.102.22
                 8.8.8.8
    DNS Domain: maas

In this case, this script will get 192.168.102.22 for systems that
comes with systemd-resolve, but the test will fail with:
    Could not resolve 'security.ubuntu.com'

Using the Current DNS Server instead can solve this issue. But this
property does not exist before Focal. The solution is to use
resolvectl by default and parse for "Current DNS Server", while still
using the systemd-resolve to parse for "DNS Servers" in older release.

Patch tested with X/B/F/I on bare-metal MAAS, F/J on Intel MAAS

Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 ubuntu_fan_smoke_test/smoke_test_old.sh | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/ubuntu_fan_smoke_test/smoke_test_old.sh b/ubuntu_fan_smoke_test/smoke_test_old.sh
index 990a6804..8ad8ae54 100755
--- a/ubuntu_fan_smoke_test/smoke_test_old.sh
+++ b/ubuntu_fan_smoke_test/smoke_test_old.sh
@@ -142,16 +142,16 @@ fanatic_docker_test()
 	dns_opt=""
 	dns1=$(awk '$1=="nameserver"{print $2; exit}' /etc/resolv.conf)
 	if [ "$dns1" = "127.0.0.53" ]; then
-		if command -v systemd-resolve 2>&1 > /dev/null; then
+		if command -v resolvectl 2>&1 > /dev/null; then
+			dns_opt="--dns=$(resolvectl status |
+				sed -n "0,/Current DNS/s/^.*Current DNS Server: //p")"
+		else
 			dns_opt="--dns=$(systemd-resolve --status |
 				awk '/DNS Servers:/{
 					sub(/.*DNS Servers: */, "")
 					sub(/,.*/, "")
 					print
 					exit}')"
-		else
-			dns_opt="--dns=$(resolvectl status |
-				sed -n "0,/Current DNS/s/^.*Current DNS Server: //p")"
 		fi
 		echo -n "($dns_opt): "
 	else
-- 
2.25.1