Don't rely on tap's local time and target servers time to do a timeout

[visch]

          We shouldn't rely on a local time to compare with the time on the postgres server. Can we instead just record the current time stamp on the local machine and then compare the current timestamp here to see if 5 seconds has elapsed instead of worrying about the timestamp from postgres? This way we don't need to work about skew

Originally posted by @visch in #249 (comment)