This migrates the above files from tempest. This includes tempest
commits:
* certificates_client.py : Ia97c34f15aa06e11434ea9f66359adbca75bd9d4
* test_certificates_client.py: I3ad6761651cec5e66012d08e6b63322f53286a5c
* certificates.py : Ica929c402a3d042ae751302384e68853eb28b405
to see the commit history for these files refer to the above sha1s
in the tempest repository
Partially implements blueprint migrate-service-clients-to-tempest-lib
Change-Id: I225569ddb2c56200cf071e7abd017ce183fd161f