Previously the start was that of the first child node.

From CPython 3.8.2, the range of an attribute access `(expr).blah`
 includes the leading parenthesis, and thus starts before `expr`.

The range of kdev-python's Attribute node represents only the range of
 `blah`, and is calculated in an awkward way.

When an attribute access of a parenthesized expression appeared at the
 start of a file, the start of the attribute range from CPython was
 before that of the CodeAst node (based on the start of `expr`)
 resulting in an incorrect range being calculated.

This case is very unusual in real code, but fixes the tests. ;-)