test: enable the missing Host header ListBuckets test

Since fasthttp v1.70.0 an HTTP/1.1 request without a Host header is
rejected and the gateway answers it with 400 BadRequest. Add a server
test that sends such requests over a raw connection and stop skipping
the REST missing host test against the gateway.

Fixes #1530

tests/test_rest_list_buckets.sh

@@ -105,9 +105,6 @@ export RUN_USERS=true
 
 # tags: openssl,ListBuckets,required-headers,host,invalid-header
 @test "REST - missing host parameter" {
-  if [ "$DIRECT" != "true" ]; then
-    skip "https://github.com/versity/versitygw/issues/1530"
-  fi
   run send_openssl_go_command "400" "-missingHostParam"
   assert_success
 }