oslib-posix: rename socket_set_nonblock() to qemu_set_nonblock()

The fcntl(fd, F_SETFL, O_NONBLOCK) flag is not specific to sockets.
Rename to qemu_set_nonblock() just like qemu_set_cloexec().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/block/sheepdog.c b/block/sheepdog.c
index bb67c4c..987018e 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -471,7 +471,7 @@
         qerror_report_err(err);
         error_free(err);
     } else {
-        socket_set_nonblock(fd);
+        qemu_set_nonblock(fd);
     }
 
     return fd;