[FAB-3776] unit test get config after restart

Added unit tests to cover the scenario described in
the comments of https://gerrit.hyperledger.org/r/#/c/9185/

Change-Id: I204eaf1adb60a8e8ffa24d3b87b68c483ea9f832
Signed-off-by: Luis Sanchez <sanchezl@us.ibm.com>

orderer/multichain/chainsupport_test.go

@@ -131,7 +131,6 @@ func TestWriteLastConfig(t *testing.T) {
 
 	cm.SequenceVal = 1
 	expected = uint64(2)
-
 	if lc := utils.GetLastConfigIndexFromBlockOrPanic(cs.WriteBlock(cb.NewBlock(2, nil), nil, nil)); lc != expected {
 		t.Fatalf("Second block should have config block index of %d, but got %d", expected, lc)
 	}
@@ -140,4 +139,21 @@ func TestWriteLastConfig(t *testing.T) {
 		t.Fatalf("Second block should have config block index of %d, but got %d", expected, lc)
 	}
 
+	t.Run("ResetChainSupport", func(t *testing.T) {
+
+		cm.SequenceVal = 2
+		expected = uint64(4)
+
+		cs = &chainSupport{ledgerResources: &ledgerResources{configResources: &configResources{Manager: cm}, ledger: ml}, signer: mockCrypto()}
+
+		if lc := utils.GetLastConfigIndexFromBlockOrPanic(cs.WriteBlock(cb.NewBlock(4, nil), nil, nil)); lc != expected {
+			t.Fatalf("Second block should have config block index of %d, but got %d", expected, lc)
+		}
+
+		if lc := utils.GetLastConfigIndexFromBlockOrPanic(cs.WriteBlock(cb.NewBlock(5, nil), nil, nil)); lc != expected {
+			t.Fatalf("Second block should have config block index of %d, but got %d", expected, lc)
+		}
+
+	})
+
 }