Description of problem:

```
[root@cloudhost ~]# rpm -q atomic docker 
atomic-1.18.1-3.fc26.x86_64
docker-1.13.1-13.git51eb16e.fc26.x86_64
[root@cloudhost ~]# rpm-ostree status
State: idle
Deployments:
● fedora-atomic:fedora/26/x86_64/atomic-host
             Version: 26.64 (2017-06-15 12:41:33)
              Commit: 0b10663541dfecafb9e78b91f6c56a86eeec2ddab8edbddc89de2fce32b7b4a1


[root@cloudhost ~]# atomic --debug install --system --name etcd gscrivano/etcd 
Namespace(_class=<class 'Atomic.install.Install'>, args=[], assumeyes=False, debug=True, display=False, func='install', ignore=False, image='gscrivano/etcd', name='etcd', opt1=None, opt2=None, opt3=None, profile=False, remote=None, setvalues=None, storage=None, system=True, system_package='auto', user=False)
Pulling layer b6d7751a6ff4fb76b26e37f859c5d1a1b7ec1b100a2e97ca67a10d03943efbeb
Pulling layer c3e1f3cb80b133fe779ee14082096fdd728f5adb6a55242df1a98345025b9df5
Pulling layer 3144e25dda39743814c2772fae603ace99267093365e15cc02fae19a8b53e88b
Pulling layer a97b5627595558549ddcf6f28603cf6a733539c610e4275006065644b6b3f161
Pulling layer 8c1c4e1f949b32e3c82c57e36021b8f425a731cf26b1ceea457560e621c3eb29
Pulling layer 6bbaeb5ae04b1f24520ae0eb3f0d6d6024c5641a9cc329a3637ab33b88391573
Extracting to /var/lib/containers/atomic/etcd.0
expected str, bytes or os.PathLike object, not NoneType
Traceback (most recent call last):
  File "/usr/bin/atomic", line 203, in <module>
    sys.exit(_func())
  File "/usr/lib/python3.6/site-packages/Atomic/install.py", line 132, in install
    return be.install(self.image, self.name)
  File "/usr/lib/python3.6/site-packages/Atomic/backends/_ostree.py", line 127, in install
    return self.syscontainers.install(image, name)
  File "/usr/lib/python3.6/site-packages/Atomic/syscontainers.py", line 227, in install
    return_value = self._install(image, name)
  File "/usr/lib/python3.6/site-packages/Atomic/syscontainers.py", line 367, in _install
    self._checkout(repo, name, image, 0, False, values=values, remote=self.args.remote, system_package=self.args.system_package)
  File "/usr/lib/python3.6/site-packages/Atomic/syscontainers.py", line 471, in _checkout
    system_package=system_package)
  File "/usr/lib/python3.6/site-packages/Atomic/syscontainers.py", line 817, in _do_checkout
    shutil.copyfile(unitfileout, os.path.join(prefix, destination, "%s.service" % name))
  File "/usr/lib64/python3.6/posixpath.py", line 78, in join
    a = os.fspath(a)
TypeError: expected str, bytes or os.PathLike object, not NoneType

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/atomic", line 231, in <module>
    sys.exit(1)
SystemExit: 1
```


Expected results:


Additional info: