Code review comment for lp:~lool/linaro-image-tools/testsuite-when-installed

Followup IRC chat:

15:09 < james_w> lool, We have to be very careful to use a matching
                 linaro-hwpack-create for our linaro-image-tools.

15:10 < james_w> lool, so when looking for that command, I think we should
                 always take one from next to the linaro-image-tools script,
                 before searching $PATH
15:10 < james_w> I think your change will approximate that in most cases, but
                 I'm not sure if it goes far enough to be robust
15:11 < lool> james_w: So you're saying, additionally to all things I've
              listed, we should first look for linaro-hwpack-* in the directory
              where linaro-media-create is, then fallback to PATH?
15:13 < james_w> lool, that's what I think
15:13 < lool> james_w: It makes sense
15:14 < lool> james_w: albeit I can think that if you have multiple
              linaro-hwpack-*, then you probably also have multiple python
              modules, and you're asking for trouble if PYTHONPATH and PATH
              don't point at the same versions in the same order
15:14 < james_w> lool, indeed
15:15 < lool> james_w: Do you still want this covered? We could do it either
              by passing directories across calls, or by prepending PATH
              immediately
15:15 < lool> But prepending PATH might have side effects when looking for
              other commands

15:16 < james_w> lool, right, I imagine it should just be for
                 linaro-hwpack-install