Fix fixture "imports_on_separate_lines1".

The fix had nothing to do and the input file was the same as the
output file.
Fix: fix "imports_on_separate_lines" kills leading comment.

This happened for any comment preceding an import statement on
no-indent-level, if the statement is processed by this fix. Blank
lines between the comment and the import statement did not matter.
Fix: fix "imports_on_separate_lines" indents wrong after other stmt.

If the import-stmt is indented, but not the first statement in the
block, the indent was lost.

As a side-effect, this change also reverts the last change, since
both cases are now handled the same.