LU-13141 ldiskfs: block alloc performance patch

LU-13141 ldiskfs: block alloc performance patch

Add block alloc performance patch to CentOS 7.7, 8.0 and
Ubuntu 19.04 5.0 kernel.

Cray-bug-id: LUS-8402
Signed-off-by: Shaun Tancheff <stancheff@cray.com>
Change-Id: Ifeb78839e5dbe8731bbb5532906708b97d4d9d33
Reviewed-on: https://review.whamcloud.com/37250
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Artem Blagodarenko <c17828@cray.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>