Merged the get_read_fd and get_write_fd requests.

diff --git a/server/snapshot.c b/server/snapshot.c
index 0a690eb..ae4eb49 100644
--- a/server/snapshot.c
+++ b/server/snapshot.c
@@ -47,8 +47,7 @@
     NULL,                         /* satisfied */
     NULL,                         /* get_poll_events */
     NULL,                         /* poll_event */
-    no_read_fd,                   /* get_read_fd */
-    no_write_fd,                  /* get_write_fd */
+    no_get_fd,                    /* get_fd */
     no_flush,                     /* flush */
     no_get_file_info,             /* get_file_info */
     snapshot_destroy              /* destroy */