Logcli query --tail incorrectly handles --since/--from

[chancez]

Describe the bug
Logcli incorrectly sets the wrong query parameter for specifying the start time of a tail query, making --since/--from ineffective.

To Reproduce

~/p/loki(⎈ |dev-2447-us-west-2:monitoring) czibolski ❯❯❯ logcli --addr=https://loki.example.com query --no-labels '{doesnt="matter"}' --since 1s --tail                                                                                                                               master ✭ ✱ ◼
2021-01-29 12:23:13.546125 I | proto: duplicate proto type registered: ingester.Series
wss://loki.example.com/loki/api/v1/tail?delay_for=0&from=1611951792546900000&limit=30&query=%7Bdoesnt%3D%22matter%22%7D

Notice the query param from is used. It should be start according the API docs https://grafana.com/docs/loki/latest/api/#get-lokiapiv1tail.

This results in all logcli query --tail requests to default to showing the last 1 hour of logs.

Expected behavior
Logcli sets the start query parameter instead, properly filtering the logs based on the --since/--from time.

Environment:

~/p/loki(⎈ |dev-2447-us-west-2:monitoring) czibolski ❯❯❯ logcli --version                                                                                                                                                                                                                   master ✭ ✱ ◼
2021-01-29 12:26:20.504350 I | proto: duplicate proto type registered: ingester.Series
logcli, version 2.1.0 (branch: HEAD, revision: 1b79df37)
  build user:       root@b8941a81fe55
  build date:       2020-12-24T14:08:17Z
  go version:       go1.15.3
  platform:         darwin/amd64