GET /timezone no longer sets to system

The original design for timezone intentionally set the system timezone
based on geoip results, before a POST /timezone.  After the feedback on
LP: #1936310 I'm having second thoughts on that and wish for GET to be
a simple informational query with no such side effects.

subiquity/server/controllers/timezone.py

@@ -108,16 +108,17 @@ class TimeZoneController(SubiquityController):
             timedatectl_settz(self.app, self.model.timezone)
 
     async def GET(self) -> TimeZoneInfo:
+        # if someone POSTed before, return that
         if self.model.timezone:
             return TimeZoneInfo(self.model.timezone,
                                 self.model.got_from_geoip)
 
-        # a bare call to GET() is equivalent to autoinstall "timezone: geoip"
-        self.deserialize('geoip')
-        tz = self.model.timezone
-        if not tz:
-            tz = timedatectl_gettz()
-        return TimeZoneInfo(tz, self.model.got_from_geoip)
+        # GET requests geoip results
+        if self.app.geoip.timezone:
+            return TimeZoneInfo(self.app.geoip.timezone, True)
+
+        # geoip wasn't ready for some reason, so ask the system
+        return TimeZoneInfo(timedatectl_gettz(), False)
 
     async def POST(self, tz: str):
         self.deserialize(tz)

subiquity/tests/test_timezonecontroller.py

@@ -14,7 +14,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import mock
-import subprocess
 
 from subiquity.common.types import TimeZoneInfo
 from subiquity.models.timezone import TimeZoneModel
@@ -102,3 +101,9 @@ class TestTimeZoneController(SubiTestCase):
         self.tzc.app.dry_run = True
         self.tzc.deserialize('geoip')
         self.assertEqual('sleep', subprocess_run.call_args.args[0][0])
+
+    @mock.patch('subiquity.server.controllers.timezone.timedatectl_settz')
+    def test_get_tz_should_not_set(self, tdc_settz):
+        run_coro(self.tzc.GET())
+        self.assertFalse(self.tzc.model.should_set_tz)
+        tdc_settz.assert_not_called()