[FAB-12205] fix data race creating fs blocksItr

updateCheckpoint can run concurrent with the construction of a blocks
iterator. When this happens, serialization is needed between the update
of the checkpoint info and the read done by the construction of the
iterator.

Change-Id: I4fba0400820abd2c6d7c511286a8382b801563e9
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>

common/ledger/blkstorage/fsblkstorage/blocks_itr.go

@@ -33,6 +33,8 @@ type blocksItr struct {
 }
 
 func newBlockItr(mgr *blockfileMgr, startBlockNum uint64) *blocksItr {
+	mgr.cpInfoCond.L.Lock()
+	defer mgr.cpInfoCond.L.Unlock()
 	return &blocksItr{mgr, mgr.cpInfo.lastBlockNumber, startBlockNum, nil, false, &sync.Mutex{}}
 }