make deleteWithObjects() work with empty containers

As is, deleteWithObjects() will fail if container is EMPTY. This is because an object count of zero means $secondsToWait = 0, which means $endTime = time(), which means WHILE loop never runs. Quickest solution was to change "time() __<__ $endTime" to "time() __<=__ $endTime" on line 192, but it makes more sense to just delete the container if it's empty.
Cool, once you send in that fix to this PR, the build should pass on Travis CI and we should be good to merge after that!