Mock out time.sleep in storwize unit tests

The Storwize driver has issues that required them
to add a sleep 1 on init of the driver.

No big deal, but causes unit tests to take a very long
time waiting for the "time.sleep(1)" on every single
unit test that calls init.

This patch just mocks out the time.sleep so we don't have
to do the silly waiting in unit tests.

Change-Id: I10fc3d00252a7e7b90085cb308fb9c6c7e1f5ea7