Revert "mvcc: test inflight Hash to trigger Size on nil db"

This reverts commit 994e8e4.

Since now etcdserver gracefully shuts down the gRPC server

mvcc/kvstore_test.go

@@ -518,20 +518,6 @@ func newTestKeyBytes(rev revision, tombstone bool) []byte {
 	return bytes
 }
 
-// TestStoreHashAfterForceCommit ensures that later Hash call to
-// closed backend with ForceCommit does not panic.
-func TestStoreHashAfterForceCommit(t *testing.T) {
-	be, tmpPath := backend.NewDefaultTmpBackend()
-	kv := NewStore(be, &lease.FakeLessor{}, nil)
-	defer os.Remove(tmpPath)
-
-	// as in EtcdServer.HardStop
-	kv.Close()
-	be.Close()
-
-	kv.Hash()
-}
-
 func newFakeStore() *store {
 	b := &fakeBackend{&fakeBatchTx{
 		Recorder:   &testutil.RecorderBuffered{},