Fix sync not downloading queued objects on first sync of session

`firstInSession` wasn't being properly set, so previously failed data
objects weren't being retried until a manual sync. Local files also
weren't being scanned for changes for three hours, but that's probably
better in the age of DB-stored annotations, so leave that off for now
and address properly in #5025.

chrome/content/zotero/xpcom/storage/storageEngine.js

@@ -149,7 +149,9 @@ Zotero.Sync.Storage.Engine.prototype.start = Zotero.Promise.coroutine(function*
 	// full check of this library, check only files that were previously modified or opened
 	// recently
 	else if (this.background
-			&& !this.firstInSession
+			// TEMP: Don't check all files at startup
+			// https://github.com/zotero/zotero/issues/5025
+			//&& !this.firstInSession
 			&& this.local.lastFullFileCheck[libraryID]
 			&& (this.local.lastFullFileCheck[libraryID]
 				+ (this.maxCheckAge * 1000)) > new Date().getTime()) {

chrome/content/zotero/xpcom/sync/syncRunner.js

@@ -230,7 +230,7 @@ Zotero.Sync.Runner_Module = function (options = {}) {
 					}
 				}.bind(this),
 				background: !!options.background,
-				firstInSession: _firstInSession,
+				firstInSession: options.firstInSession,
 				resetMode: options.resetMode
 			};