drivers/raw_exec: restore ability to run tasks without nomad running as root (#18206)

Although nomad officially does not support running the client as a non-root
user, doing so has been more or less possible with the raw_exec driver as
long as you don't expect features to work like networking or running tasks
as specific users. In the cgroups refactoring I bulldozed right over the
special casing we had in place for raw_exec to continue working if the cgroups
were unable to be created. This PR restores that behavior - you can now
(as before) run the nomad client as a non-root user and make use of the
raw_exec task driver.

client/lib/proclib/wrangler.go

@@ -43,8 +43,10 @@ func (w *Wranglers) Setup(task Task) error {
 	// create process wrangler for task
 	pw := w.create(task)
 
-	// perform any initialization if necessary
-	pw.Initialize()
+	// perform any initialization if necessary (e.g. create cgroup)
+	// if this doesn't work just keep going; it's up to each task driver
+	// implementation to decide if this is a failure mode
+	_ = pw.Initialize()
 
 	w.lock.Lock()
 	defer w.lock.Unlock()

drivers/shared/executor/executor.go

@@ -315,8 +315,8 @@ func (e *UniversalExecutor) Launch(command *ExecCommand) (*ProcessState, error)
 
 	// setup containment (i.e. cgroups on linux)
 	if cleanup, err := e.configureResourceContainer(command, os.Getpid()); err != nil {
-		e.logger.Error("failed to configure resource container", "error", err)
-		return nil, err
+		// keep going; some folks run nomad as non-root and expect this driver to still work
+		e.logger.Warn("failed to configure container, process isolation will not work", "error", err)
 	} else {
 		defer cleanup()
 	}

e2e/vaultcompat/vaultcompat_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/hashicorp/go-set"
 	"github.com/hashicorp/go-version"
 	nomadapi "github.com/hashicorp/nomad/api"
+	"github.com/hashicorp/nomad/helper/testlog"
 	"github.com/hashicorp/nomad/testutil"
 	vaultapi "github.com/hashicorp/vault/api"
 	"github.com/shoenig/test/must"
@@ -135,7 +136,7 @@ func startNomad(t *testing.T, vc *vaultapi.Client) (func(), *nomadapi.Client) {
 		c.Client = &testutil.ClientConfig{
 			Enabled: true,
 		}
-		c.LogLevel = "off"
+		c.LogLevel = testlog.HCLoggerTestLevel().String()
 	})
 	nc, err := nomadapi.NewClient(&nomadapi.Config{
 		Address: "http://" + ts.HTTPAddr,