Exception activating extension due to telemetry persistence

```
2019-09-17 23:33:00 [ERROR]: Error Activating AWS Toolkit TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined
at validateString (internal/validators.js:125:11)
at Object.join (path.js:1147:7)
at new DefaultTelemetryService (/tmp/vscode-extensions/amazonwebservices.aws-toolkit-vscode@1.0.0/extension/out/src/shared/telemetry/defaultTelemetryService.js:31:37)
at /tmp/vscode-extensions/amazonwebservices.aws-toolkit-vscode@1.0.0/extension/out/src/extension.js:80:48
at Generator.next ()
at fulfilled (/tmp/vscode-extensions/amazonwebservices.aws-toolkit-vscode@1.0.0/extension/out/src/extension.js:8:58)
at process._tickCallback (internal/process/next_tick.js:68:7)
```

Tested on theia

Potential cause: globalStoragePath may be undefined?

Start with the activation stack trace and inspect DefaultTelemetryService at extension/out/src/shared/telemetry/defaultTelemetryService.js:31, then follow its construction from extension/out/src/extension.js:80. Reproduce activation on Theia and verify that telemetry persistence no longer fails because of an undefined path.

Written by the indexing model from the issue text.