ci: limit gotestsum to circle ci

Part 2 of breaking up https://github.com/hashicorp/nomad/pull/12255

This PR makes it so gotestsum is invoked only in CircleCI. Also the
HCLogger(t) is plumbed more correctly in TestServer and TestAgent so
that they respect NOMAD_TEST_LOG_LEVEL.

The reason for these is we'll want to disable logging in GHA,
where spamming the disk with logs really drags performance.

command/agent/testagent.go

@@ -16,6 +16,7 @@ import (
 	metrics "github.com/armon/go-metrics"
 	"github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/nomad/api"
+	client "github.com/hashicorp/nomad/client/config"
 	"github.com/hashicorp/nomad/client/fingerprint"
 	"github.com/hashicorp/nomad/helper/freeport"
 	"github.com/hashicorp/nomad/helper/testlog"
@@ -357,6 +358,14 @@ func (a *TestAgent) config() *Config {
 	config := nomad.DefaultConfig()
 	conf.NomadConfig = config
 
+	// Setup client config
+	conf.ClientConfig = client.DefaultConfig()
+
+	logger := testlog.HCLogger(a.T)
+	conf.LogLevel = testlog.HCLoggerTestLevel().String()
+	conf.NomadConfig.Logger = logger
+	conf.ClientConfig.Logger = logger
+
 	// Set the name
 	conf.NodeName = a.Name