Fix disambiguation to consider steps with different fully-qualified names different.
Fix disambiguation to consider steps with different fully-qualified names different.

This is a port of the following tools/build CL:
https://codereview.chromium.org/1315253005

BUG=
CC=machenbach@chromium.org
TBR=iannucci@chromium.org

Review URL: https://codereview.chromium.org/1335943004 .

luci/recipes-py,luci/recipes-py,shishkander/recipes-py,shishkander/recipes-py