This PR adds the import statement to fix cluster creation error
and enables flake8-f821 rule checks.
F821 rule checks "undefined name"
Original problem:
we have currently got `NameError: name 'common_glance' is not defined`
error when creating a cluster because I failed to edit the patch[1].
Co-Authored-By: wu.chunyang <wchy1001@gmail.com>
[1]: 2f52b2fddb
Story: 2010151
Task: 45797
Change-Id: I846f433ff35a9638a070382bf89e02db617dcd3d