Update 'edx' group to 'adm' group in LMS setup

* Use the 'adm' group for permissioning assets needed during LMS
  initialization, because ubuntu doesn't have the edx user until it logs
  out and logs back in.
Merge pull request #40 from edx/bugfix/jrbl/permissioning_in_vpc

Update 'edx' group to 'adm' group in LMS setup