RIL is allowed to set bandwidth to zero


git-svn-id: https://gnunet.org/svn/gnunet@32385 140774ce-b5e7-0310-ab8b-a85725594a96
transport's idea of being notified about an explicitc disconnect using bw 0/0 and the modification of the ril solver 
to allocate 0 bandwidth do not work together at the moment
this is problem of semantic and not of implementation


git-svn-id: https://gnunet.org/svn/gnunet@32386 140774ce-b5e7-0310-ab8b-a85725594a96