(PUP-1459) Add support for root_home on OS X 10.9

getent does not exist on 10.9 so this commit uses
dscacheutil to query the homedir for the root user.
Merge pull request #215 from blkperl/add_root_home_to_mavericks

(PUP-1459) Add support for root_home on OS X 10.9