scanner: fix bug with indent at start of node.

scanner: fix bug with indent at start of node.

If we find an indent, we assume there are delayed newlines
to comsume.
This is often true, but not at the start of a node.
So don't decrement delayed_lines if it is already zero.

Add the test case that found this bug for me.

Signed-off-by: NeilBrown <neil@brown.name>