block testtools 1.2.0

We're now seeing the following failure in all tempest runs:

subunit.run discover: error: no such option: --list

This coincides with testtools 1.2.0 release, so block it to try to get
everything functioning again.

Change-Id: I2f8737b44c703c3094d6bbb6580993f86a571934
Exclude testtools 1.4.0

When running tempest with testtools 1.4.0 attributes aren't being added to the
test_id. This causes the regex excludes we use for the slow tests in tempest to not
work, and the slow jobs get run everywhere, while the slow jobs fail to have any tests. 

Change-Id: I561e98bf363d2dd8e8b3a20cea7d2dcbfa034e98