[conformal/btcwire] bd2974: Make var length string overflow tests consistent.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcwire
  Commit: bd297491b9ccc5611057abf9c3f43199dedeb7f0
      
https://github.com/conformal/btcwire/commit/bd297491b9ccc5611057abf9c3f43199dedeb7f0
  Author: Dave Collins <da...@conformal.com>
  Date:   2013-10-25 (Fri, 25 Oct 2013)

  Changed paths:
    M common_test.go

  Log Message:
  -----------
  Make var length string overflow tests consistent.

This commit modifies the variable length string overflow tests slight to
make them consistent with the other overflow tests.