perf: Clean up Hoststack tests

- Update test names with clients/streams
- Convert test results to JSON output
  * iperf3 results include bits_per_second
  * vpp_echo results include both client
    and server output which includes time in seconds
    and rx_data/tx_data in bytes which can be used
    to calculate the average bits per second.
    Tx and Rx data will always be the same:
    BPS = (client tx_data * 8) / ((client time + server time) / 2)
- Fix WRK test results data formatting errors

Change-Id: Ie2aeb665e3cc0739b16f97ba2628eebe6e041d22
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>