Remove hardcoded /tftpboot/ from token's tftp path

Since file to be fetched from the root tftp directory it shouldn't
contain any hardcoded path. Additionaly it eliminates bearing with
map-file containing regular expressions for tftp path replacement.

Change-Id: Iee1672834f735d7dfefce43000540522e1d053b9
Closes-Bug: #1291533
Merge "Remove hardcoded /tftpboot/ from token's tftp path"