fix(ci): require correct socket module (#13026)

require 'socket.unix' was causing a different socket module to be loaded

If 'socket.unix' was loaded before the `socket` module, it resulted
in a different socket implementation to be used, which resulted in
failures when trying to access nil fields of the socket object.

More info: https://konghq.atlassian.net/browse/KAG-4472

(cherry picked from commit a212d89)

spec/busted-ci-helper.lua

@@ -12,6 +12,10 @@
 -- FAILED_TEST_FILES_FILE environment variable.  This is used to
 -- reduce test rerun times for flaky tests.
 
+
+-- needed before requiring 'socket.unix'
+require 'socket'
+
 local busted = require 'busted'
 local cjson = require 'cjson'
 local socket_unix = require 'socket.unix'