LU-14139 ptlrpc: grow reply buffer properly for batch request

LU-14139 ptlrpc: grow reply buffer properly for batch request

This patch adds the support to grow the reply buffer for batch
PtlRPC request.
With this support, statahead sanity-pfl test for test_16b will
pass for large LOV stripes with overstriping.

Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: Iaa7eb88b49d6ee068ec1fd9666a8bac2839b5041
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/40945
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Mikhail Pershin <mpershin@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>