[FIX] website_blog: do not show current blog post as next post
[FIX] website_blog: do not show current blog post as next post

At the bottom of each blog post there is a link to the next blog post
of the blog. If the current blog post is the last, the next blog post
which appears is the first one, which is ok. However, if there is only
one blog post in the blog, when viewing it, the next blog post which
was proposed was the current one (now nothing is proposed as next blog
post anymore).

dfang/odoo,dfang/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,dfang/odoo,dfang/odoo,dfang/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,dfang/odoo