ADB Backup: fix adb restore issues

Set Backup_FileName on adb backup to fix restore.
Set read_from_adb after EOF to return properly
from newer adb client prompt.
Create setter and getter for Backup_FileName
for openrecoveryscript.cpp which is not a
friend class.
Fix condition for twrpTar::Get_Size() and adb backup.
Change-Id: I7eb8168fa3416366b996e220cecbc0e1bcec5e8e