[Chromoting] Fix telemetry error in remoting.It2MeActivity
[Chromoting] Fix telemetry error in remoting.It2MeActivity

1. Excludes the access code entry time from the session duration.
2. Reports cancellation/error to the telemetry service if the
   main promise in It2meActivity.start() rejects.
3. Disposes DesktopRemotingActivity if the session fails to connect.

BUG=549658

Review URL: https://codereview.chromium.org/1413923015

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#358874}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk