Update Dockerfile
Update Dockerfile

* Remove duplication
* make sure we go back to /tmp each time
Guokr1991/POCS,AstroHuntsman/POCS,panoptes/POCS,AstroHuntsman/POCS,AstroHuntsman/POCS,panoptes/POCS,Guokr1991/POCS,panoptes/POCS,Guokr1991/POCS,fmin2958/POCS,fmin2958/POCS,fmin2958/POCS,joshwalawender/POCS,AstroHuntsman/POCS,joshwalawender/POCS,joshwalawender/POCS,panoptes/POCS,Guokr1991/POCS