[BUG] vcsim: -method-delay does not work

[Syuparn]

Describe the bug
vcsim option -method-delay does not work and created tasks are completed immediately.

To Reproduce
Steps to reproduce the behavior:

1. run vcsim: vcsim -method-delay "PowerOff:10000"
2. create a new task: govc vm.power -off -force DC0_H0_VM0
3. get current tasks: govc tasks | grep PowerOff

Expected behavior
A clear and concise description of what you expected to happen.

There is a running PowerOff task.

$ govc tasks | grep PowerOff
PowerOff                                 vm-55                          vcsim                           11:41:11  running

Affected version
Please provide details on the version used, e.g. release tag, commit, module version, etc.

• vcsim 0.34.1

Screenshots/Debug Output
If applicable, add screenshots or debug output to help explain your problem.

PowerOff task succeeds instantly.

$ govc tasks | grep PowerOff
PowerOff                                 vm-55                          vcsim                           11:41:11  11:41:11  11:41:11 success [654.214µs]

Additional context
When the task PowerOffVM_Task is delayed instead of PowerOff, it will wait as specified by -method-delay. However the task will not appear until it has completed.

# delay PowerOffVM_Task for 10 seconds
$ vcsim -method-delay "PowerOffVM_Task:10000"
# This takes 10 seconds to get response
$ govc vm.power -off -force DC0_H0_VM0
Powering off VirtualMachine:vm-55... OK

$ govc tasks | grep PowerOff
# 10 seconds later
$ govc tasks | grep PowerOff
PowerOff                                 vm-55                          vcsim                           11:44:56  11:44:56  11:44:56 success [811.876µs]