Add single redo for failed tests

Closes #261 (closed)

To help confirm if results are a blip or not

    █ API - Project Repository File Raw

    data_received..............: 418 MB  7.0 MB/s
    data_sent..................: 160 kB  2.7 kB/s
    group_duration.............: avg=1728.16ms min=495.31ms med=1496.94ms max=12595.69ms p(90)=2715.90ms p(95)=3286.02ms
    http_req_blocked...........: avg=3.40ms    min=0.00ms   med=0.00ms    max=112.89ms   p(90)=0.01ms    p(95)=0.01ms
    http_req_connecting........: avg=3.39ms    min=0.00ms   med=0.00ms    max=112.80ms   p(90)=0.00ms    p(95)=0.00ms
    http_req_duration..........: avg=1688.55ms min=495.18ms med=1451.65ms max=12452.04ms p(90)=2676.54ms p(95)=3225.97ms
    http_req_receiving.........: avg=1459.33ms min=297.72ms med=1220.54ms max=12227.22ms p(90)=2453.73ms p(95)=2993.91ms
    http_req_sending...........: avg=0.02ms    min=0.01ms   med=0.02ms    max=0.11ms     p(90)=0.03ms    p(95)=0.04ms
    http_req_tls_handshaking...: avg=0.00ms    min=0.00ms   med=0.00ms    max=0.00ms     p(90)=0.00ms    p(95)=0.00ms
  ✓ http_req_waiting...........: avg=229.20ms  min=189.77ms med=226.16ms  max=327.92ms   p(90)=256.80ms  p(95)=283.68ms
  ✗ http_reqs..................: 631     10.51664/s
    iteration_duration.........: avg=1725.44ms min=0.18ms   med=1494.48ms max=12595.70ms p(90)=2714.01ms p(95)=3285.41ms
    iterations.................: 631     10.51664/s
  ✓ successful_requests........: 100.00% ✓ 631  ✗ 0
    vus........................: 1       min=1  max=20
    vus_max....................: 20      min=20 max=20

time="2020-06-09T12:17:25+01:00" level=error msg="some thresholds have failed"
Test failed. Retrying...