libxc: restore: reset I/O fd to flags to back to state caller passed us

libxc: restore: reset I/O fd to flags to back to state caller passed us

In particular this causes us to turn O_NONBLOCK back off if we set it.

The caller may continue to use the fd for it's own protocol needs and
may not be prepared to have it become non-blocking.

This probably only effects Remus now after my previous patch to signal
the last checkpoint, since a regular migration will no longer set the
fd non-blocking.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Brendan Cully <brendan@cs.ubc.ca>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>