--watch doesn't work in combinationwith --start

**When I execute:**

awslogs get /ecs/log-name --s 10m -w

**What I expect:**
Return last 10 minutes of logs and then continue show up logs in mode --watch

**What I will get instead:**
Only last 10 minutes of logs is returned, any new logs aren't appearing.

**Am I sure about that?**
Yes I'm. It was quadruplechecked.

Reproduce the issue with `awslogs get /ecs/log-name --s 10m -w`, then trace the command-line handling for `--start` and `--watch`. Done means the command first returns the last 10 minutes of logs and then continues displaying newly arriving logs in watch mode.

Written by the indexing model from the issue text.