[libcalamares] Expand testing of TZ location lookup

- Cape Town is in South Africa, so one might expect it to get South
  Africa's timezone -- which is Africa/Johannesburg -- but Windhoek
  is closer, so it gets that.
- Port Elisabeth is similar: Maseru lies between it an Johannesburg,
  so it gets the wrong timezone, too.

These both illustrate how the limited resolution of the map, together
with the "closest location" lookup, can give poor results. For most
of South Africa, the "wrong" timezone is closer than the right one.

src/libcalamares/locale/Tests.cpp

@@ -402,6 +402,11 @@ LocaleTests::testLocationLookup_data()
     QTest::newRow( "Tarawa E" ) << 0.0 << 179.0 << QString( "Tarawa" );
     QTest::newRow( "Tarawa W" ) << 0.0 << -179.0 << QString( "Tarawa" );
 
+    QTest::newRow( "Johannesburg" ) << -26.0 << 28.0 << QString( "Johannesburg" );  // South Africa
+    QTest::newRow( "Maseru" ) << -29.0 << 27.0 << QString( "Maseru" );  // Lesotho
+    QTest::newRow( "Windhoek" ) << -22.0 << 17.0 << QString( "Windhoek" );  // Namibia
+    QTest::newRow( "Port Elisabeth" ) << -33.0 << 25.0 << QString( "Johannesburg" );  // South Africa
+    QTest::newRow( "Cape Town" ) << -33.0 << 18.0 << QString( "Johannesburg" );  // South Africa
 }
 
 void