container: Fix Delete on nonexistent container

Delete needs to release names related to a container even if that
container isn't present in the db. However, slightly overzealous error
checking causes the transaction to get rolled back. Ignore the error
from Delete on the container itself, since it may not be present.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

container/view.go

@@ -168,9 +168,9 @@ func (db *memDB) Delete(c *Container) error {
 			txn.Delete(memdbNamesTable, nameAssociation{name: name})
 		}
 
-		if err := txn.Delete(memdbContainersTable, NewBaseContainer(c.ID, c.Root)); err != nil {
-			return err
-		}
+		// Ignore error - the container may not actually exist in the
+		// db, but we still need to clean up associated names.
+		txn.Delete(memdbContainersTable, NewBaseContainer(c.ID, c.Root))
 		return nil
 	})
 }

container/view_test.go

@@ -150,4 +150,12 @@ func TestNames(t *testing.T) {
 
 	view = db.Snapshot()
 	assert.Equal(t, map[string][]string{"containerid1": {"name1", "name3", "name4"}, "containerid4": {"name2"}}, view.GetAllNames())
+
+	// Release containerid1's names with Delete even though no container exists
+	assert.NoError(t, db.Delete(&Container{ID: "containerid1"}))
+
+	// Reusing one of those names should work
+	assert.NoError(t, db.ReserveName("name1", "containerid4"))
+	view = db.Snapshot()
+	assert.Equal(t, map[string][]string{"containerid4": {"name1", "name2"}}, view.GetAllNames())
 }