Replaced animation of Refresh-Icon in Actionbar at Activity MailList.

With this commit, the refresh-icon at the mail list will not be replaced with another spinning Icon (that looks totally different), it will now just start rotating.

It has no effect on Android versions below HoneyComb. I don't think this is a big deal, because now the Animations are also different.

If this Commit gets pulled, I will also make this change at the other activities like at the Folders list.