Flake8: Fix some occurences of F841

Fix F841 in some files:
F841 local variable 'XXX' is assigned to but never used

Also fix in utils.py some occurences of:
H405  multi line docstring summary not separated with an empty line

Change-Id: I272f075d874e2a48da102d9d4025cb93225170e0
Partial-Bug: #1333290