MM-13185: Fix Message Export config special case. (#9898)

It should only apply when setting through the System Console, to avoid
messing up externally managed config files.

model/config_test.go

@@ -360,6 +360,7 @@ func TestMessageExportSetDefaults(t *testing.T) {
 }
 
 func TestMessageExportSetDefaultsExportEnabledExportFromTimestampNil(t *testing.T) {
+	// Test retained as protection against regression of MM-13185
 	mes := &MessageExportSettings{
 		EnableExport: NewBool(true),
 	}
@@ -367,12 +368,13 @@ func TestMessageExportSetDefaultsExportEnabledExportFromTimestampNil(t *testing.
 
 	require.True(t, *mes.EnableExport)
 	require.Equal(t, "01:00", *mes.DailyRunTime)
-	require.NotEqual(t, int64(0), *mes.ExportFromTimestamp)
+	require.Equal(t, int64(0), *mes.ExportFromTimestamp)
 	require.True(t, *mes.ExportFromTimestamp <= GetMillis())
 	require.Equal(t, 10000, *mes.BatchSize)
 }
 
 func TestMessageExportSetDefaultsExportEnabledExportFromTimestampZero(t *testing.T) {
+	// Test retained as protection against regression of MM-13185
 	mes := &MessageExportSettings{
 		EnableExport:        NewBool(true),
 		ExportFromTimestamp: NewInt64(0),
@@ -381,7 +383,7 @@ func TestMessageExportSetDefaultsExportEnabledExportFromTimestampZero(t *testing
 
 	require.True(t, *mes.EnableExport)
 	require.Equal(t, "01:00", *mes.DailyRunTime)
-	require.NotEqual(t, int64(0), *mes.ExportFromTimestamp)
+	require.Equal(t, int64(0), *mes.ExportFromTimestamp)
 	require.True(t, *mes.ExportFromTimestamp <= GetMillis())
 	require.Equal(t, 10000, *mes.BatchSize)
 }
@@ -425,6 +427,7 @@ func TestMessageExportSetDefaultsExportDisabledExportFromTimestampZero(t *testin
 }
 
 func TestMessageExportSetDefaultsExportDisabledExportFromTimestampNonZero(t *testing.T) {
+	// Test retained as protection against regression of MM-13185
 	mes := &MessageExportSettings{
 		EnableExport:        NewBool(false),
 		ExportFromTimestamp: NewInt64(12345),
@@ -433,7 +436,7 @@ func TestMessageExportSetDefaultsExportDisabledExportFromTimestampNonZero(t *tes
 
 	require.False(t, *mes.EnableExport)
 	require.Equal(t, "01:00", *mes.DailyRunTime)
-	require.Equal(t, int64(0), *mes.ExportFromTimestamp)
+	require.Equal(t, int64(12345), *mes.ExportFromTimestamp)
 	require.Equal(t, 10000, *mes.BatchSize)
 }