Branch:HEAD

b=13570
In filter_check_grant, for non_grant cache write, we should
check the left space by  if (*left > ungranted + bytes), instead
of (*left > ungranted), because only we are sure the left space
is enough for another "bytes", then the ungrant space should be
increase. In client, we should update cl_avail_grant only there is
OBD_MD_FLGRANT in the reply.
i=adilger,green