fix(bulk): honor ignoreUndefined in initializeUnorderedBulkOp

* initializeUnorderedBulkOp to honor ignoreUndefined

All write operations (insertOne,update,updateMany etc...). honor the ignoreUndefined flag defined in the collection scope. Apparently UnorderedBulkOp was left out. This fixes it, makes UnorderedBulkOp honor the flag.

* Fix lint

* Add ignoreUndefined option to initializeOrderedBulkOp

* Fix comment lower case

* Give function's options precedence over session's options.

lib/collection.js

@@ -2048,11 +2048,17 @@ Collection.prototype.mapReduce = function(map, reduce, options, callback) {
  * @param {(number|string)} [options.w] The write concern.
  * @param {number} [options.wtimeout] The write concern timeout.
  * @param {boolean} [options.j=false] Specify a journal write concern.
+ * @param {boolean} [options.ignoreUndefined=false] Specify if the BSON serializer should ignore undefined fields.
  * @param {ClientSession} [options.session] optional session to use for this operation
  * @return {UnorderedBulkOperation}
  */
 Collection.prototype.initializeUnorderedBulkOp = function(options) {
   options = options || {};
+  // Give function's options precedence over session options.
+  if (options.ignoreUndefined == null) {
+    options.ignoreUndefined = this.s.options.ignoreUndefined;
+  }
+
   options.promiseLibrary = this.s.promiseLibrary;
   return unordered(this.s.topology, this, options);
 };
@@ -2066,11 +2072,16 @@ Collection.prototype.initializeUnorderedBulkOp = function(options) {
  * @param {number} [options.wtimeout] The write concern timeout.
  * @param {boolean} [options.j=false] Specify a journal write concern.
  * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {boolean} [options.ignoreUndefined=false] Specify if the BSON serializer should ignore undefined fields.
  * @param {OrderedBulkOperation} callback The command result callback
  * @return {null}
  */
 Collection.prototype.initializeOrderedBulkOp = function(options) {
   options = options || {};
+  // Give function's options precedence over session's options.
+  if (options.ignoreUndefined == null) {
+    options.ignoreUndefined = this.s.options.ignoreUndefined;
+  }
   options.promiseLibrary = this.s.promiseLibrary;
   return ordered(this.s.topology, this, options);
 };