AWS: Decrease current size only once

[johanneswuerbach]

Deleting a placeholder instance introduced in #2235 seems to decrease the in-memory ASG size twice, once in the deletion loop itself and once in decreaseAsgSizeByOneNoLock, which calls setAsgSizeNoLock and also updates the curSize

This is actually not causing issues yet, as the ASG cache is force refreshed after a deletion now

autoscaler/cluster-autoscaler/cloudprovider/aws/aws_manager.go

Lines 283 to 284 in c3c9fc1

	klog.V(2).Infof("Some ASG instances might have been deleted, forcing ASG list refresh")
	return m.forceRefresh()

.

I still added a test to confirm that deleting placeholders actually works as expected.

//cc @piontec

[johanneswuerbach]

/assign @Jeffwan
/assign @piontec

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/assign @piontec

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[Jeffwan]

It looks good to me. hold for a while and see if @piontec has other options.

[Jeffwan]

/lgtm

[losipiuk]

/approve

[losipiuk]

/lgtm
/approve
Thanks!

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[losipiuk]

@Jeffwan sorry for merging this. I did not notice you asked @piontec to take a look at that too. Let me know if you feel we should revert the change for now.

[Jeffwan]

@losipiuk Didn't hear back from @piontec yet. It's fine to merge it and I don't see problems .

[piontec]

Sorry for the delay, yes, it was definitely OK to merge.