Fix backport.pl so it doesn't ignore the Branch if the value ends in /.
Fix backport.pl so it doesn't ignore the Branch if the value ends in /.

* tools/dist/backport.pl
  (sanitize_branch): Be less greedy with removing leading characters by using
    the $BRANCHES constant to find the start of the branch.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1541813 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion