dlm: use fixed errno values in messages

Some errno values differ across platforms. So if we return things like
-EINPROGRESS from one node it can get misinterpreted or rejected on
another one.

This patch fixes up the errno values passed on the wire so that they
match the x86 ones (so as not to break the protocol), and re-instates
the platform-specific ones at the other end.

Many thanks to Fabio for testing this patch.
Initial patch from Patrick.

Signed-off-by: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Fabio M. Di Nitto <fabbione@ubuntu.com>
Signed-off-by: David Teigland <teigland@redhat.com>