LU-14881 libcfs: Complete testing for tcp_sock_set_*

LU-14881 libcfs: Complete testing for tcp_sock_set_*

Linux commits:
  v5.7-rc6-2504-gddd061b8daed
  tcp: add tcp_sock_set_quickack

  v5.7-rc6-2508-gd41ecaac903c
  tcp: add tcp_sock_set_keepintvl

  v5.7-rc6-2509-g480aeb9639d6
  tcp: add tcp_sock_set_keepcnt

Introduced a series of helper functions that may be
back ported individually.

Lustre-change: https://review.whamcloud.com/44374
Lustre-commit: bbd9646f91fd13ea84f730296f3ce6983030aea2

Test-Parameters: trivial
Fixes: 99d9638d6c ("LU-13783 libcfs: support removal of kernel_setsockopt()")
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I4fce67b801979ec7857265b6bd0370c05737e268
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Aurelien Degremont <degremoa@amazon.com>
Reviewed-on: https://review.whamcloud.com/44995
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Andreas Dilger <adilger@whamcloud.com>