Always use busybox for docker permission fix

gns3server/modules/docker/docker_vm.py

@@ -402,7 +402,7 @@ class DockerVM(BaseVM):
                 "/gns3/bin/busybox",
                 "sh",
                 "-c",
-                "(/gns3/bin/busybox find \"{path}\" -depth -print0 | xargs -0 stat -c '%a:%u:%g:%n' > \"{path}/.gns3_perms\") && /gns3/bin/busybox chmod -R u+rX \"{path}\" && /gns3/bin/busybox chown {uid}:{gid} -R \"{path}\"".format(uid=os.getuid(), gid=os.getgid(), path=volume))
+                "(/gns3/bin/busybox find \"{path}\" -depth -print0 | /gns3/bin/busybox xargs -0 /gns3/bin/busybox stat -c '%a:%u:%g:%n' > \"{path}/.gns3_perms\") && /gns3/bin/busybox chmod -R u+rX \"{path}\" && /gns3/bin/busybox chown {uid}:{gid} -R \"{path}\"".format(uid=os.getuid(), gid=os.getgid(), path=volume))
             yield from process.wait()
 
     @asyncio.coroutine

tests/modules/docker/test_docker_vm.py

@@ -926,5 +926,5 @@ def test_fix_permission(vm, loop):
     process = MagicMock()
     with asyncio_patch("asyncio.subprocess.create_subprocess_exec", return_value=process) as mock_exec:
         loop.run_until_complete(vm._fix_permissions())
-    mock_exec.assert_called_with('docker', 'exec', 'e90e34656842', '/gns3/bin/busybox', 'sh', '-c', '(/gns3/bin/busybox find "/etc" -depth -print0 | xargs -0 stat -c \'%a:%u:%g:%n\' > "/etc/.gns3_perms") && /gns3/bin/busybox chmod -R u+rX "/etc" && /gns3/bin/busybox chown {}:{} -R "/etc"'.format(os.getuid(), os.getgid()))
+    mock_exec.assert_called_with('docker', 'exec', 'e90e34656842', '/gns3/bin/busybox', 'sh', '-c', '(/gns3/bin/busybox find "/etc" -depth -print0 | /gns3/bin/busybox xargs -0 /gns3/bin/busybox stat -c \'%a:%u:%g:%n\' > "/etc/.gns3_perms") && /gns3/bin/busybox chmod -R u+rX "/etc" && /gns3/bin/busybox chown {}:{} -R "/etc"'.format(os.getuid(), os.getgid()))
     assert process.wait.called