remove pre-0.9 driver code and related E2E test

.changelog/12791.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+drivers: removed support for restoring tasks created before Nomad 0.9
+```

drivers/docker/driver.go

@@ -185,11 +185,6 @@ func (d *Driver) RecoverTask(handle *drivers.TaskHandle) error {
 		return nil
 	}
 
-	// COMPAT(0.10): pre 0.9 upgrade path check
-	if handle.Version == 0 {
-		return d.recoverPre09Task(handle)
-	}
-
 	var handleState taskHandleState
 	if err := handle.GetDriverState(&handleState); err != nil {
 		return fmt.Errorf("failed to decode driver task state: %v", err)

drivers/exec/driver.go

@@ -375,11 +375,6 @@ func (d *Driver) RecoverTask(handle *drivers.TaskHandle) error {
 		return fmt.Errorf("handle cannot be nil")
 	}
 
-	// COMPAT(0.10): pre 0.9 upgrade path check
-	if handle.Version == 0 {
-		return d.recoverPre09Task(handle)
-	}
-
 	// If already attached to handle there's nothing to recover.
 	if _, ok := d.tasks.Get(handle.Config.ID); ok {
 		d.logger.Trace("nothing to recover; task already exists",

drivers/java/driver.go

@@ -378,11 +378,6 @@ func (d *Driver) RecoverTask(handle *drivers.TaskHandle) error {
 		return fmt.Errorf("handle cannot be nil")
 	}
 
-	// COMPAT(0.10): pre 0.9 upgrade path check
-	if handle.Version == 0 {
-		return d.recoverPre09Task(handle)
-	}
-
 	// If already attached to handle there's nothing to recover.
 	if _, ok := d.tasks.Get(handle.Config.ID); ok {
 		d.logger.Debug("nothing to recover; task already exists",

drivers/qemu/driver.go

@@ -269,11 +269,6 @@ func (d *Driver) RecoverTask(handle *drivers.TaskHandle) error {
 		return fmt.Errorf("error: handle cannot be nil")
 	}
 
-	// COMPAT(0.10): pre 0.9 upgrade path check
-	if handle.Version == 0 {
-		return d.recoverPre09Task(handle)
-	}
-
 	// If already attached to handle there's nothing to recover.
 	if _, ok := d.tasks.Get(handle.Config.ID); ok {
 		d.logger.Trace("nothing to recover; task already exists",

drivers/rawexec/driver.go

@@ -246,11 +246,6 @@ func (d *Driver) RecoverTask(handle *drivers.TaskHandle) error {
 		return fmt.Errorf("handle cannot be nil")
 	}
 
-	// COMPAT(0.10): pre 0.9 upgrade path check
-	if handle.Version == 0 {
-		return d.recoverPre09Task(handle)
-	}
-
 	// If already attached to handle there's nothing to recover.
 	if _, ok := d.tasks.Get(handle.Config.ID); ok {
 		d.logger.Trace("nothing to recover; task already exists",