Modify getting of primary storage size

Settings application shows internal storage size using API getTotalBytes in StorageStatsManager.
This API calls getPrimaryStorageSize() in StorageManager.
getPrimaryStorageSize() returns /data parition size calculated API roundStorageSize() in FileUtils.
Using this API, total primary storage size returns 8GB if 16GB emmc size device has /data partition size below 8GB.
So we should modify getting of primary storage size close to real emmc size.
getPrimaryStorageSize() will be calculated sum of /data and /system partition size.

Test: Check primary storage size in Settings application

Change-Id: I3ad33534b1c55d09afbb0e9be1c408c02c442842
Signed-off-by: hj.seo <hj.seo@lge.com>