Ignore ansible-lint command exit code

This patch disables the ansible-lint check by ignoring the command exit
code.

Signed-off-by: Gael Chamoulaud (Strider) <gchamoul@redhat.com>
Change-Id: Idc345bb16456b4092ece0c1ed21800b64c2586ba

tox.ini

@@ -37,7 +37,7 @@ commands = oslo_debug_helper {posargs}
 [testenv:ansible-lint]
 basepython = python2
 commands =
-  bash tools/ansible-lint.sh
+  - bash tools/ansible-lint.sh
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.