Fix an on-screen representation glitch.

Fix an on-screen representation glitch.

If a layout has NextNoIndent set to true, the following paragraph
is not indented on screen. LyX checks the previous layout for that
style parameter to decide whether to indent or not. Of course,
what matters is the latex output and the on-screen representation
should match this output. Now, when a layout has NextNoIndent==true,
the latex output is correctly not indented, while the on-screen
representation may fail to match this output. This can occur when,
for example, a standard paragraph is nested in the previous layout,
because LyX would check the property of the nested layout instead
of the container layout. Thus, LyX should check the property of a
previous layout at the same depth for correctly deciding whether
a paragraph has to be indented or not.
See also http://www.lyx.org/trac/ticket/9055#comment:12 for an
example document where the previous scenario actually occurs.