Add negative test to verify fail to fetch the file resource with non-FIPS algorithms

According to https://github.com/coreos/coreos-assembler/pull/4477#issuecomment-4156120051, https://github.com/coreos/coreos-assembler/pull/4477#issuecomment-4091519907, https://github.com/coreos/coreos-assembler/pull/4477#issuecomment-4091846830

When testing this, we do not need both the client & server to be FIPS enabled to have a valid TLS connection, just care about the part you control to be in FIPS mode.

PR https://github.com/coreos/coreos-assembler/pull/4373 (enable FIPS on client) covers the test that Ignition config fetch file from the FIPS-compliant nginx, we need to add a negative test, that verifies that attempting to use algorithms that aren't FIPS compliant nginx will make the connection fail.

The steps are:

• On server side (none FIPS):

Build nginx container, add ssl_ecdh_curve X25519 in nginx.conf, that means: When a client connects, I want to use the X25519 curve to negotiate the encryption keys (that is none FIPS-compliant).
Run nginx

• On client (enable FIPS):
  Start with FIPS enabled, use ignition to fetch file from server failed

See the details in https://hackmd.io/6KV-LsE3QReu34nQQOgruA?view

Review PR 4373 and the linked HackMD for the existing FIPS-enabled client test and test entry point. Build the non-FIPS nginx container with ssl_ecdh_curve X25519, run it, then exercise Ignition with a FIPS-enabled client. Done means the file fetch fails when the server requires the non-FIPS algorithm.