Try to report source of bad Lua API calls
test-server: only listen to 127.0.0.1

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
Lua scripting: improve error reporting.

When calling Lua scripts we try to report not just the error but
information about the code line causing the error.
Lua script errors format more unified.

lua_pcall error handler now formats errors in a way more similar to
luaPushError() so that errors generated in different contexts look alike.