staging: lustre: llite: handle xattr cache refill race

staging: lustre: llite: handle xattr cache refill race

In ll_xattr_cache_refill() if the xattr cache was invalid (and no
request was sent) then return -EAGAIN so that ll_getxattr_common()
caller will fetch the xattr from the MDT.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-10132
Reviewed-on: https://review.whamcloud.com/29654
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>