Tests: SSL certificates

Parallel/sharding groups often fail to create certificates in CI.
Most likely it is related to the fact they use the same directory
for certificates. This commit uses a different directory per group

Author: dcorbacho

deps/rabbitmq_ct_helpers/src/rabbit_ct_helpers.erl

@@ -597,9 +597,13 @@ ensure_rabbitmq_queues_cmd(Config) ->
 
 ensure_ssl_certs(Config) ->
     SrcDir = ?config(rabbitmq_ct_helpers_srcdir, Config),
+    Group = proplists:get_value(name,
+                                ?config(tc_group_properties, Config)),
     CertsMakeDir = filename:join([SrcDir, "tools", "tls-certs"]),
     PrivDir = ?config(priv_dir, Config),
-    CertsDir = filename:join(PrivDir, "certs"),
+    CertsDir = filename:join([PrivDir, Group, "certs"]),
+    _ = filelib:ensure_dir(CertsDir),
+    _ = file:make_dir(CertsDir),
     CertsPwd = proplists:get_value(rmq_certspwd, Config, ?SSL_CERT_PASSWORD),
     Cmd = [
       "PASSWORD=" ++ CertsPwd,