util: try to set with SO_{RCV,SND}BUFFORCE when requested size is larger than the kernel limit

The commit 10ce2e06 inverts the order of
SO_{RCV,SND}BUFFORCE and SO_{RCV,SND}BUF. However, setting buffer size with
SO_{RCV,SND}BUF does not fail even if the requested size is larger than
the kernel limit. Hence, SO_{RCV,SND}BUFFORCE will not use anymore and
the buffer size is always limited by the kernel limit even if we have
the priviledge to ignore the limit.

This makes the buffer size is checked after configuring it with
SO_{RCV,SND}BUF, and if it is still not sufficient, then try to set it
with FORCE command. With this commit, if we have enough priviledge, the
requested buffer size is correctly set.

Hopefully fixes #14417.