replace addtional deprecated methods in mongodb adapter

Author: nanov

lib/store/databases/mongodb.js

@@ -352,13 +352,13 @@ _.extend(Mongo.prototype, {
       return callback(err);
     }
 
-    this.store.update({ _id: sagaId, '_commands.id': cmdId }, { $pull: { '_commands': { id: cmdId } } }, { safe: true }, function (err) {
+    this.store.updateOne({ _id: sagaId, '_commands.id': cmdId }, { $pull: { '_commands': { id: cmdId } } }, { safe: true }, function (err) {
       if (callback) callback(err);
     });
   },
 
   clear: function (callback) {
-    this.store.remove({}, { safe: true }, callback);
+    this.store.deleteMany({}, { safe: true }, callback);
   }
 
 });