CA-94829: Set the TCP timeout properties on the migration fd

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
CA-97883: Wrap the fstat call in an exception handler

We can get an exception when we're fstatting a file that's larger
than is representable in a signed 32-bit integer (ie., 2 gigs).
If this happens, it's clearly not a socket, so don't bother setting
the TCP timeout parameters.

This patch is actually a bit more defensive, and ignores any
exception thrown here.

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>

Conflicts:
	ocaml/xenguest/xenguest_main.ml
Merge pull request #1094 from jonludlam/CA-94829-clearwater

CLEARWATER: CA-94829 clearwater