migration-tcp: call migrate_fd_error() instead of close() and free().

migration-tcp: call migrate_fd_error() instead of close() and free().

This patch fixes the following error report.  When changing
migration-tcp.c to call migrate_fd_error() instead of close() and
free() by itself, monitor is resumed, and returns allocated mig_state
is set to current_migration in migration.c allows us to print "info
migrate".

Reported-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>