Revert "Try to fix travis build by using a proper IP address for testing"

Using a test IP address as per RFC 5737 may lead to Errno::ENETUNREACH
instead of Errno::ETIMEDOUT, so it does not fix the test on travis.

This reverts commit adaee1501ffbe7c93c26c63c17dbcb2dfff686fa.
Increase :start_timeout for ftp server in integration test