LU-12276 lnet: check const parameters for ib_post_send and ib_post_recv

In MOFED 4.6, the second and third parameters for ib_post_send() and
ib_post_recv() are declared with 'const'. This patch adds the check in
configure file to resolve build failure.

Change-Id: If7193a6a4fcb7b238f5d4ee64e878a5816433e7b
Test-Parameters: trivial
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34837
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sonia Sharma <sharmaso@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>