Change db schema of package_info table

Change db schema of package_info table

pkg_id cannot be used as primary key because the case of symlink exist
in package path. On symlink existing case, pkg id will be same on both
of symlink path and original path(resolved path) so it could be conflict
on package_info table with same pkg_id.

Change-Id: Iaf9580c5979ad6bcb32170743d47c34602295c16
Signed-off-by: Kyungwook Tak <k.tak@samsung.com>