test: applying timezone is asynchronous

So, we need to try to read timezone several times.
Also, on failure, show journal of timedated instead of hostnamed,
as the timezone is handled by timedated.

Hopefully fixes #33007.

(cherry picked from commit 1ef586a)
(cherry picked from commit 91d31ca)
(cherry picked from commit 8b86ada)

Author: yuwata

test/networkd-test.py

@@ -1040,13 +1040,16 @@ def get_tz():
         self.create_iface(dhcpserver_opts='EmitTimezone=yes\nTimezone=Pacific/Honolulu')
         self.do_test(coldplug=None, extra_opts='IPv6AcceptRA=false\n[DHCP]\nUseTimezone=true', dhcp_mode='ipv4')
 
-        # should have applied the received timezone
-        try:
-            self.assertEqual(get_tz(), 'Pacific/Honolulu')
-        except AssertionError:
+        # Should have applied the received timezone. This is asynchronous, so we need to wait for a while:
+        for _ in range(20):
+            tz = get_tz()
+            if tz == 'Pacific/Honolulu':
+                break
+            time.sleep(0.5)
+        else:
             self.show_journal('systemd-networkd.service')
-            self.show_journal('systemd-hostnamed.service')
-            raise
+            self.show_journal('systemd-timedated.service')
+            self.fail(f'Timezone: {tz}, expected: Pacific/Honolulu')
 
 
 class MatchClientTest(unittest.TestCase, NetworkdTestingUtilities):