Use PyMySQL as MySQL DB driver for unit tests
Use PyMySQL as MySQL DB driver for unit tests

MySQL-python is not supported and is not compatible with python3.

Change-Id: I9df8666697f11c966018ae3b3fa52be4c614edd5

esikachev/sahara-tests,openstack/sahara-scenario,openstack/sahara-tests,esikachev/sahara-tests,openstack/sahara-tests,esikachev/sahara-tests,openstack/sahara-scenario,openstack/sahara-tests,openstack/sahara-tests,openstack/sahara-scenario