scripts: Remove unused variables in all Python scripts

Discovered with pylint3.

Use the placeholder name '_' for unproblematic unused variables. It's
what I'm used to, and pylint knows not to flag it.

Python tip:

    for i in range(n):
        some_list.append(0)

can be replaced with

    some_list += n*[0]

Similarly, 3*'\t' gives '\t\t\t'.

(Relevant here because pylint flagged the loop index as unused.)

To do integer division in Python 3, use // instead of /.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>

scripts/sanity_chk/harness.py

@@ -56,7 +56,7 @@ class Console(Harness):
                 if self.ordered:
                     ordered = True
                     pos = 0
-                    for k,v in self.matches.items():
+                    for k in self.matches:
                         if k != self.regex[pos]:
                             ordered = False
                         pos += 1