fix(pylint): Escape backslash properly

fix(pylint): Escape backslash properly

When backslach is used to escape Robot dollar or docstring asterisk,
and the backslash is in normal (not raw) Python (doc)string,
the backslash itself needs to be escaped by a second backslash.

The old code happened to work well enough,
but now it leads to a loud SyntaxWarning in console log,
so it is worth fixing faster than other pylint violations.

Change-Id: Id36fa0a393267f2cdced1229a30eaff8357c4ac4
Signed-off-by: Vratko Polak <vrpolak@cisco.com>