Revert "libvmclient: Take VmCallback in VmInstance::start()"

Revert submission 3408863

Reason for revert: Likely culprit for b/391356639  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Reverted changes: /q/submissionid:3408863

Change-Id: Id9436b9557e0fd4cbc94df9f22ba35132619aa91
diff --git a/microfuchsia/microfuchsiad/src/instance_starter.rs b/microfuchsia/microfuchsiad/src/instance_starter.rs
index 7c4f32d..e3c4e8d 100644
--- a/microfuchsia/microfuchsiad/src/instance_starter.rs
+++ b/microfuchsia/microfuchsiad/src/instance_starter.rs
@@ -96,6 +96,7 @@
             console_in,
             /* log= */ None,
             /* dump_dt= */ None,
+            None,
         )
         .context("Failed to create VM")?;
         if let Some(pty) = &pty {
@@ -104,7 +105,7 @@
                 .setHostConsoleName(&pty.follower_name)
                 .context("Setting host console name")?;
         }
-        vm_instance.start(None).context("Starting VM")?;
+        vm_instance.start().context("Starting VM")?;
 
         Ok(MicrofuchsiaInstance {
             _vm_instance: vm_instance,