server: create pause rootfs manually without Docker

This lessens the Docker requirement for creating sandboxes (with the
requirement only existing for the actual image pulling that is done when
adding a container to a pod). The interface was chosen to match the
--conmon interface, so that the location of the pause binary can be
chosen by a user.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

server/server.go

@@ -27,6 +27,7 @@ type Server struct {
 	root         string
 	runtime      *oci.Runtime
 	sandboxDir   string
+	pausePath    string
 	stateLock    sync.Mutex
 	state        *serverState
 	netPlugin    ocicni.CNIPlugin
@@ -107,7 +108,7 @@ func (s *Server) releasePodName(name string) {
 }
 
 // New creates a new Server with options provided
-func New(runtimePath, root, sandboxDir, containerDir string, conmonPath string) (*Server, error) {
+func New(runtimePath, root, sandboxDir, containerDir, conmonPath, pausePath string) (*Server, error) {
 	// TODO: This will go away later when we have wrapper process or systemd acting as
 	// subreaper.
 	if err := utils.SetSubreaper(1); err != nil {
@@ -139,6 +140,7 @@ func New(runtimePath, root, sandboxDir, containerDir string, conmonPath string)
 		runtime:    r,
 		netPlugin:  netPlugin,
 		sandboxDir: sandboxDir,
+		pausePath:  pausePath,
 		state: &serverState{
 			sandboxes:  sandboxes,
 			containers: containers,