Description:add a private flag to mark an elf file, and remove obsolete cached pages before writing on a elf file

Team:OTHERS
Feature or Bugfix:Bugfix
Binary Source:NA
PrivateCode(Yes/No):No

Change-Id: If3a17ac05c5035045704a0b66307165ab0076c34
Reviewed-on: http://mgit-tm.rnd.huawei.com/10334851Reviewed-by: Ncaoruihong 00546070 <crh.cao@huawei.com>
Reviewed-by: Nshenwei 00579521 <denny.shenwei@huawei.com>
Tested-by: Npublic jenkins <public_jenkins@notesmail.huawei.com>