Wait to unmount propagatedmount before marking plugin as disabled.

TestPluginTrustedInstall revealed a race in the plugin shutdown logic,
where the exit channel signal was sent even before the propagated mounts
were unmounted. If the same plugin was enabled, it would try to setup
propagated mounts *before* it was unmounted resulting in errors.

This change fixes the behavior by waiting until the unmount completes on
disable before marking the plugin as disabled.

Signed-off-by: Anusha Ragunathan <anusha.ragunathan@docker.com>
Upstream-commit: 70b76266b586d193c333aa37dcda031f3d89f108
Component: engine

components/engine/plugin/manager.go

@@ -131,15 +131,6 @@ func (pm *Manager) StateChanged(id string, e libcontainerd.StateInfo) error {
 			return err
 		}
 
-		pm.mu.RLock()
-		c := pm.cMap[p]
-
-		if c.exitChan != nil {
-			close(c.exitChan)
-		}
-		restart := c.restart
-		pm.mu.RUnlock()
-
 		os.RemoveAll(filepath.Join(pm.config.ExecRoot, id))
 
 		if p.PropagatedMount != "" {
@@ -152,6 +143,14 @@ func (pm *Manager) StateChanged(id string, e libcontainerd.StateInfo) error {
 			}
 		}
 
+		pm.mu.RLock()
+		c := pm.cMap[p]
+		if c.exitChan != nil {
+			close(c.exitChan)
+		}
+		restart := c.restart
+		pm.mu.RUnlock()
+
 		if restart {
 			pm.enable(p, c, true)
 		}