az acr task run to minimize output

**Describe the bug**
running `az acr task run` generates a lot of debugging information. Should move this to `--debug` execution, or otherwise minimize the noise

**To Reproduce**
Steps to reproduce the behavior:
```sh
az acr run -r contosobaseimages --cmd "mcr.microsoft.com/azure-cli az --version" /dev/null
```
generates:
```sh
Queued a run with ID: ca5
Waiting for an agent...
2019/10/08 21:56:20 Creating Docker network: acb_default_network, driver: 'bridge'
2019/10/08 21:56:20 Successfully set up Docker network: acb_default_network
2019/10/08 21:56:20 Setting up Docker configuration...
2019/10/08 21:56:21 Successfully set up Docker configuration
2019/10/08 21:56:21 Logging in to registry: contosobaseimages.azurecr.io
2019/10/08 21:56:23 Successfully logged into contosobaseimages.azurecr.io
2019/10/08 21:56:23 Executing step ID: acb_step_0. Timeout(sec): 600, Working directory: '', Network: 'acb_default_network'
2019/10/08 21:56:23 Launching container with name: acb_step_0
Unable to find image 'mcr.microsoft.com/azure-cli:latest' locally
latest: Pulling from azure-cli
Digest: sha256:1c366c415bd5b085e0e94c61bdc7abc136f5667c32c4e4c9ddab8b8b996e4a4a
Status: Downloaded newer image for mcr.microsoft.com/azure-cli:latest
```
**Expected behavior**
Minimized output
```sh
2019/10/08 21:56:20 Queued a run with ID: ca5
2019/10/08 21:56:20 Waiting for an agent...
2019/10/08 21:56:23 Executing step ID: acb_step_0. Timeout(sec): 600, Working directory: '', Network: 'acb_default_network'
Unable to find image 'mcr.microsoft.com/azure-cli:latest' locally
latest: Pulling from azure-cli
Digest: sha256:1c366c415bd5b085e0e94c61bdc7abc136f5667c32c4e4c9ddab8b8b996e4a4a
Status: Downloaded newer image for mcr.microsoft.com/azure-cli:latest
```