Gate fix: Cap hacking to avoid gate failure

hacking is not capped in g-r and it is in
blacklist for requirement as hacking new version
can break the gate jobs.

Hacking can break gate jobs because of various
reasons:
- There might be new rule addition in hacking
- Some rules becomes default from non-default
- Updates in pycodestyle etc

That was the main reason it was not added in g-r
auto sync also. Most of the project maintained the
compatible and cap the hacking version in
test-requirements.txt and update to new version when
project is ready. Bumping new version might need code
fix also on project side depends on what new in that
version.

If project does not have cap the hacking version then,
there is possibility of gate failure whenever new hacking
version is released by QA team.

Example of such failure in recent release of hacking 1.1.0
- http://lists.openstack.org/pipermail/openstack-dev/2018-May/130282.html

Change-Id: I05790c5f946a4127fe6c8d9867cc618cb83d67fb

test-requirements.txt

@@ -7,7 +7,7 @@ beautifulsoup4>=4.6.0 # MIT
 coverage!=4.4,>=4.0 # Apache-2.0
 doc8>=0.6.0 # Apache-2.0
 extras>=1.0.0 # MIT
-hacking>=0.10.0
+hacking>=0.10.0,<1.1.0
 openstackdocstheme>=1.18.1 # Apache-2.0
 oslo.log>=3.36.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0