MM-16725 Respect env var overrides when setting config (#11821)

* Respect env var overrides when setting config

* Use strings.NewReader

api4/apitestlib.go

@@ -64,7 +64,7 @@ func UseTestStore(store store.Store) {
 func setupTestHelper(enterprise bool, updateConfig func(*model.Config)) *TestHelper {
 	testStore.DropAllTables()
 
-	memoryStore, err := config.NewMemoryStore()
+	memoryStore, err := config.NewMemoryStoreWithOptions(&config.MemoryStoreOptions{IgnoreEnvironmentOverrides: true})
 	if err != nil {
 		panic("failed to initialize memory store: " + err.Error())
 	}

api4/config_test.go

@@ -234,6 +234,7 @@ func TestGetEnvironmentConfig(t *testing.T) {
 	os.Setenv("MM_SERVICESETTINGS_SITEURL", "http://example.mattermost.com")
 	os.Setenv("MM_SERVICESETTINGS_ENABLECUSTOMEMOJI", "true")
 	defer os.Unsetenv("MM_SERVICESETTINGS_SITEURL")
+	defer os.Unsetenv("MM_SERVICESETTINGS_ENABLECUSTOMEMOJI")
 
 	th := Setup().InitBasic()
 	defer th.TearDown()