Disable alertmanager sharding tests. (#4024)

Signed-off-by: Steve Simpson <[email protected]>

Author: stevesg

integration/alertmanager_test.go

@@ -233,6 +233,8 @@ func TestAlertmanagerClustering(t *testing.T) {
 }
 
 func TestAlertmanagerSharding(t *testing.T) {
+	t.Skip("Flaky test under investigation")
+
 	tests := map[string]struct {
 		legacyAlertStore bool
 	}{

pkg/alertmanager/multitenant_test.go

@@ -1026,6 +1026,8 @@ func TestAlertmanager_ReplicasPosition(t *testing.T) {
 }
 
 func TestAlertmanager_StateReplicationWithSharding(t *testing.T) {
+	t.Skip("Flaky test under investigation")
+
 	tc := []struct {
 		name              string
 		replicationFactor int