Remove AnsibleCommon class method mock

Remove AnsibleCommon class method mock

In [1], several methods in "AnsibleCommon" class are mocked, but those
mocks are not removed after the test execution. Depending on the test
execution order, this affects other results.

[1] https://github.com/opnfv/yardstick/blob/stable/fraser/yardstick/tests/unit/service/test_environment.py#L20

JIRA: YARDSTICK-1214

Change-Id: I85ef702b3b5b2fda5cf453a21b9f0bec61b155f0
Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
(cherry picked from commit e204c5063ab86d4ed2bff296959afae43866890f)