Merge r86398 into the old wfWaitForSlaves. Update core calls.

Merge r86398 into the old wfWaitForSlaves. Update core calls.
maintenance/waitForSlave.php still calls the old prototype.
Most instances were replaced with
sed -i 's/wfWaitForSlaves( [0-9]* );/wfWaitForSlaves();/' ./maintenance/initEditCount.php ./maintenance/updateRestrictions.php ./maintenance/updateSpecialPages.php ./maintenance/importDump.php ./maintenance/moveBatch.php ./maintenance/storage/resolveStubs.php ./maintenance/storage/trackBlobs.php ./maintenance/storage/fixBug20757.php ./maintenance/storage/moveToExternal.php ./maintenance/storage/compressOld.inc ./maintenance/populateSha1.php ./maintenance/deleteDefaultMessages.php ./maintenance/migrateUserGroup.php ./maintenance/importImages.php ./maintenance/runJobs.php ./maintenance/archives/upgradeLogging.php ./maintenance/deleteBatch.php ./maintenance/populateLogSearch.php ./maintenance/populateLogUsertext.php ./maintenance/gearman/gearmanWorker.php ./maintenance/populateRevisionLength.php ./maintenance/refreshLinks.php ./maintenance/deleteSelfExternals.php ./maintenance/upgrade1_5.php ./maintenance/rebuildFileCache.php ./includes/job/RefreshLinksJob.php ./includes/installer/MysqlUpdater.php ./maintenance/convertUserOptions.php ./maintenance/populateParentId.php ./maintenance/runBatchedQuery.php ./maintenance/upgrade1_5.php ./maintenance/waitForSlave.php ./maintenance/populateCategory.php ./maintenance/importImages.php