migration: remove double call to migrate_fd_close

The call in buffered_close is enough, because buffered_close is called
already by migrate_fd_cleanup.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

migration.c

diff --git a/migration.c b/migration.c
index 810f25e..e560930 100644
--- a/migration.c
+++ b/migration.c
@@ -272,7 +272,7 @@
         s->file = NULL;
     }
 
-    migrate_fd_close(s);
+    assert(s->fd == -1);
     return ret;
 }