LU-9319 statahead: skip agl for the file in restoring

LU-9319 statahead: skip agl for the file in restoring

In case of restore, the MDT has the right size and has already sent
it back without granting the layout lock, inode is up-to-date. Then
AGL (async glimpse lock) is useless.

Also to glimpse we need the layout, in case of a running restore the
MDT holds the layout lock so the glimpse will block up to the end of
restore (statahead/agl will block).

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Iaaf138a28671c3eccfb05b08ce8d7364423256a1
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-on: https://review.whamcloud.com/26501
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>