Fix golint warnings for daemon/execdriver/*

Addresses: #14756

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Upstream-commit: 3d17c3bb663a5d7a65bd39a5ef32cb4668b48c53
Component: engine

components/engine/daemon/execdriver/windows/unsupported.go

@@ -8,6 +8,7 @@ import (
 	"github.com/docker/docker/daemon/execdriver"
 )
 
+// NewDriver returns a new execdriver.Driver
 func NewDriver(root, initPath string) (execdriver.Driver, error) {
 	return nil, fmt.Errorf("Windows driver not supported on non-Windows")
 }