Move Cliff requirements to 2.16.0

Cliff 2.16.0 is the version supported for lower release of Tripleo.
The VF support as well this version 2.16.0 so we dont need to restrict
to an upper version.

Change-Id: I482f3596ed53be5109ad41e2e862684c258b574a

.reqcheck_override.yaml

@@ -4,3 +4,4 @@ packages:
     - name: "python-yaml"
     - name: "python-PyYAML"
     - name: "PyYAML"
+    - name: "ansible"

requirements.txt

@@ -7,4 +7,4 @@ six>=1.11.0 # MIT
 PyYAML>=3.13 # MIT
 ansible>=2.8,!=2.8.9,!=2.9.12,<2.10.0 # GPLv3+
 ansible-runner>=1.4.4 # Apache-2.0
-cliff>=3.2.0 # Apache-2.0
+cliff>=2.16.0 # Apache-2.0