Quarantine ActivityListenersAreCalled

## Failing Test(s)

- Microsoft.AspNetCore.Hosting.Tests.HostingApplicationDiagnosticsTests.ActivityListenersAreCalled

Note: this is failing in `release/6.0` so that's also where it's being quarantined.

## Error Message

```text
Assert.Equal() Failure
↓ (pos 1)
Expected: 0123456789abcdef
Actual: 0000000000000000
↑ (pos 1)
```

## Stacktrace

```text
at Microsoft.AspNetCore.Hosting.Tests.HostingApplicationDiagnosticsTests.ActivityListenersAreCalled() in /_/src/Hosting/Hosting/test/HostingApplicationDiagnosticsTests.cs:line 524
```

## Logs

```text
[xUnit.net 00:00:00.90] Microsoft.AspNetCore.Hosting.Tests.HostingApplicationDiagnosticsTests.ActivityListenersAreCalled [FAIL]
[xUnit.net 00:00:00.90] Assert.Equal() Failure
[xUnit.net 00:00:00.90] ↓ (pos 1)
[xUnit.net 00:00:00.90] Expected: 0123456789abcdef
[xUnit.net 00:00:00.90] Actual: 0000000000000000
[xUnit.net 00:00:00.90] ↑ (pos 1)
[xUnit.net 00:00:00.90] Stack Trace:
```

## Build

https://dev.azure.com/dnceng/public/_build/results?buildId=1592777