chown -R to ensure that stack user owns data_dir

The fix for bug #1129748 tightens some permissions on image
directories.  This breaks the devstack gate jobs, which were
relying on wide-open permissions.  chowning recursively should
ensure that all the directories are owned by the stack user,
so the gate tests work with tighter permissions.

Change-Id: I09be54bff6d8f9c3f7f599d6e5ada6431beb7c31
Merge "chown -R to ensure that stack user owns data_dir"