migration: add error handling to migrate_fd_put_notify().

Although migrate_fd_put_buffer() sets MIG_STATE_ERROR if it failed,
since migrate_fd_put_notify() isn't checking error of underlying
QEMUFile, those resources are kept open.  This patch checks it and
calls migrate_fd_error() in case of error.

Signed-off-by: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
