Fixes for regression test: util_http_json_encoding
This change corrects 2 bugs, causing the regression test to fail under certain circumstances:
1) use for test location [::acs::test::url] instead of [ad_url]
The call [::acs::test::url] should be used for all tests in the regression tests and avoids
problems with wrong URLs when running e.g. in a container
2) When running on a setup with self-signed certificates, the curl requests require a "-k"
flag to be passed. Otherwise, the regression test fails.