scm: mercurial: add :order => 'id DESC' explicitly for MySQL test fails.
Because :order => 'id DESC' is defined at 'has_many',
there is no need to set 'order'.
But, MySQL test fails.
Sqlite3 and PostgreSQL pass.
Is this MySQL bug?
MySQL svn trunk test on Redmine CI server fails.
But, svn 1.1-stable passes.
If this is MySQL bug, this effects 1.1-stable, too.
