dnsdist: Load Lua bindings before parsing yaml configuration

dnsdist: Load Lua bindings before parsing yaml configuration

We need the Lua bindings so that inline and loaded from a file Lua
syntax work. Our regression tests did not catch this because the
setup always created an empty Lua file, causing the Lua bindings to
be loaded. This commit also fixes that by not creating (and removing
if needed) empty Lua files in the regression tests setup.