[train] Cap hacking for py27

py27 job started to fail with new hacking versions being python3 only.
Add upper limit for this jobto the same version as neutron does in
stable/train.

Change-Id: I17509f4d6103984cf7c6e59ca6896b272eaf26ce
Closes-Bug: #1922660

test-requirements.txt

@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-hacking>=1.1.0;python_version<'3.0' # Apache-2.0
+hacking>=1.1.0,<1.2.0;python_version<'3.0' # Apache-2.0
 hacking>=3.0.1;python_version>='3.0' # Apache-2.0
 
 bandit!=1.6.0,>=1.1.0,<1.6.3;python_version<'3.0' # Apache-2.0