Add support for memory_max setting

Nomad 1.1.0 introduced a new memory_max setting enabling memory
over-subscription for tasks. This adds support for it.

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+  - Support for new `memory_max` setting
 ### Changed
   - Update to Nomad v1.1.0
   - Lower log level of passed arguments to systemd-nspawn to DEBUG

example/config.hcl

@@ -3,3 +3,8 @@ plugin "nspawn" {
     enabled = true
   }
 }
+server {
+  default_scheduler_config {
+    memory_oversubscription_enabled = true
+  }
+}

nspawn/driver.go

@@ -361,8 +361,13 @@ func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *drive
 		driverConfig.Properties = make(hclutils.MapStrStr)
 	}
 
-	if cfg.Resources.LinuxResources != nil {
-		driverConfig.Properties["MemoryMax"] = strconv.Itoa(int(cfg.Resources.LinuxResources.MemoryLimitBytes))
+	if cfg.Resources.NomadResources != nil {
+		if cfg.Resources.NomadResources.Memory.MemoryMaxMB != 0 {
+			driverConfig.Properties["MemoryHigh"] = strconv.Itoa(int(cfg.Resources.NomadResources.Memory.MemoryMB * 1024 * 1024))
+			driverConfig.Properties["MemoryMax"] = strconv.Itoa(int(cfg.Resources.NomadResources.Memory.MemoryMaxMB * 1024 * 1024))
+		} else {
+			driverConfig.Properties["MemoryMax"] = strconv.Itoa(int(cfg.Resources.NomadResources.Memory.MemoryMB * 1024 * 1024))
+		}
 	}
 
 	// Setup port mapping and exposed ports
@@ -383,10 +388,10 @@ func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *drive
 		}
 
 		if len(driverConfig.Ports) > 0 {
-			for _ , port := range driverConfig.Ports {
+			for _, port := range driverConfig.Ports {
 				p, ok := cfg.Resources.Ports.Get(port)
 				if !ok {
-					d.logger.Error("Port "+port+" not found, check network stanza")
+					d.logger.Error("Port " + port + " not found, check network stanza")
 					return nil, nil, fmt.Errorf("Port %q not found, check network stanza", port)
 				}
 				to := p.To