Revert "arc: Only call StopVm() if ARCVM is running"

This reverts commit 4bf05b95.

Reason for revert: Causing failures in ArcVmClientAdapterTest
See: https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-rel/41873

Original change's description:
> arc: Only call StopVm() if ARCVM is running
>
> This change adds a check in ArcVmClientAdapter::StopArcInstance() to see
> if a VM is running (current_cid_ is set). If not, skip calling
> ConciergeClient::StopVm() and notify observers that ARCVM is stopped
> right away.
>
> BUG=b:169893632
> TEST=arc.AuthPerf.unmanaged_vm
>
> Change-Id: Ic927f122cacea0e89cacffbbcd67a217772dba43
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462573
> Commit-Queue: Willie Koomson <wvk@google.com>
> Reviewed-by: Yusuke Sato <yusukes@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#816221}

TBR=yusukes@chromium.org,wvk@google.com

Change-Id: Ia248a8ca9bda2eee2a24bf8d23c8549fa0ae7ce8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: b:169893632
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2466501Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816254}

components/arc/session/arc_vm_client_adapter.cc

@@ -547,13 +547,6 @@ class ArcVmClientAdapter : public ArcClientAdapter,
           << "StopArcInstance is called during browser shutdown. Do nothing.";
       return;
     }
-    if (current_cid_ == kInvalidCid) {
-      // No VM is currently running, avoid calling ConciergeClient::StopVm().
-      // TODO(wvk): Once StartMiniArc() is implemented, use a DCHECK here
-      // instead.
-      OnArcInstanceStopped();
-      return;
-    }
 
     if (should_backup_log) {
       GetDebugDaemonClient()->BackupArcBugReport(