Fix for the below issue

File "/root/home/sandipd/testr_bhushana_fork/contrail-test/fixtures/nova_test.py", line 279, in create_vm
image = self.get_image(image_name=image_name)
Fi! le "/root/home/sandipd/testr_bhushana_fork/contrail-test/fixtures/nova_test.py", line 94, in get_image
got_image = self.find_image(image_name)
File "/root/home/sandipd/testr_bhushana_fork/contrail-test/fixtures/nova_test.py", line 78, in find_image
sleep(5)

NameError:
global name 'sleep' is not defined