Make /data/data a symlink to /data/user/0

For legacy reason, /data/data is a real dir and /data/user/0 is a
symbolic link to it.  Overhead for linux kernel to walk through
symbolic link is not negligible. This is unnessary overhead to
carry over.  This patch is to make /data/user/0 a a real dir and
make legacy folder /data/data a symbolic link.  OTAed system does
not get impacted.

Test: Manual test
Change-Id: I419564a75f6ebf3154badb8725ba9831164592b6
Signed-off-by: cjbao <cathy.bao@intel.com>