Enable the errorAssertions govet check for mattermost-server code (#17346)

* Enable the errorAssertions govet check for mattermost-server code

* Removing unnecesary change

* Fixing some tests

* Fixing tests

* Fixing more after merge

* Fixing new offending entries

* Fixing small vet checks

* Fixing new cases detected by govet

* Fixing remote_cluster_test errors

* Fixing assertion

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/user_test.go

@@ -118,7 +118,8 @@ func TestSetDefaultProfileImage(t *testing.T) {
 		Id:       model.NewId(),
 		Username: "notvaliduser",
 	})
-	require.Error(t, err)
+	// It doesn't fail, but it does nothing
+	require.Nil(t, err)
 
 	user := th.BasicUser