[spawn.py] Change GRAPHITE_ROOT to GRAPHITE_HOME for consistency.   The warning message was updated to make it consistent with the   actual functionality.
[spawn.py] Change GRAPHITE_ROOT to GRAPHITE_HOME for consistency.
  The warning message was updated to make it consistent with the
  actual functionality.

8l/Graphite,nkawahara/Graphite,fhijaz/Graphite,mit-carbon/Graphite,mit-carbon/Graphite,mit-carbon/Graphite,victorisildur/Graphite,8l/Graphite,victorisildur/Graphite,fhijaz/Graphite,victorisildur/Graphite,nkawahara/Graphite,8l/Graphite,fhijaz/Graphite,nkawahara/Graphite,mit-carbon/Graphite,8l/Graphite,victorisildur/Graphite,fhijaz/Graphite,nkawahara/Graphite