[vm/vmservice] Make sure writing service info file is awaited
[vm/vmservice] Make sure writing service info file is awaited

Change-Id: I57aa457fac4faf05fa8a0467d69dd4954bc481ec
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/131486
Commit-Queue: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@google.com>
Auto-Submit: Alexander Markov <239e774fd29abc1267878f57afe1a8a03e0ca887@google.com>
Reviewed-by: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk