qa/tasks: use list comprehension for checking the length

qa/tasks: use list comprehension for checking the length

instead of using filter(), use `sum()` for counting its
length, as in Python3, `filter()` actually returns a `filter` object
instead of a list.

in this change, `filter()` calls are replaced with `sum()`
for Python3 compatibility.

Signed-off-by: Kyr Shatskyy <kyrylo.shatskyy@suse.com>