Implement graceful shutdown timeout period

[liliankasem]

Issue describing the changes in this PR

resolves #4355

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• I have added all required tests (Unit tests, E2E tests)

Additional information

• Implement graceful shutdown timeout period (2 seconds) - this allows the host to gracefully shut down but will force exit if the host takes longer than the timeout period.
• Fix bug where we get a null ref error if we shut down the host during startup

[liliankasem]

@mattchenderson @fabiocav - as per @jviau suggestion, I've switched over to a grace period approach. We will give the host 2 seconds to gracefully shut down, if it does not we kill the process. The behaviour on pressing Ctrl+C remains the same where the host shutdown event is signalled and it starts its graceful shutdown process.

After we address the bug in the host, the host should shutdown with the 2 seconds pretty much every time so there shouldn't be an major impact. On the plus side, if anything ever occurs where the host does take longer, thats not something we need to worry about for local dev with the graceful timeout period.