booty: Do not strip the trailing p from a devicename like mapper/isw_Vol0_tmp
    
    While fixing bug 505205, I noticed that the code for removing the trailing p
    in a name like: mapper/isw_Vol0p1 which becomes mapper/isw_Vol0p after cutting
    is rather interesting, for example it will wrongly change the whole diskname
    mapper/isw_Vol0_tmp to mapper/isw_Vol0_tm. This patch fixes this by removing
    the trailing p as part of the partition cutting code instead of always removing
    it.