Enable flake8 E721

We already pass the test, so just remove from ignore list

Change-Id: I28bfeb99d9841532133a3825f7336e7b712d6561
Enumerate Flake8 Fxxx ignores

Instead of ignoring all Fxxx errors, ignore only the failing ones, so
its easy to fix each one separately.

Change-Id: I4ccc1d38247fb76b6dad4388b76c6e8d696f081f
Merge "Enable flake8 E721"
Merge "Enumerate Flake8 Fxxx ignores"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp