[BUGFIX release] fix issue with unchaining ChainNodes

[bekzod]

fix for #15845 #15836

[rwjblue]

Can you cherry pick the failing test commits here so that we can confirm they are passing?

[rwjblue]

Can you confirm that the regression this fixes is in 2.16? If so, can you prefix the fixing commit with [BUGFIX release] so we know to include it in the next patch release?

[bekzod]

done

[bekzod]

accidentally closed it :P

[rwjblue]

Thank you!

[krisselden]

This is poor root cause analysis, remove should never be called unbalanced, we still don't know the cause of the original regression this is just masking the symptom.

[krisselden]

we need to find the commit that caused the regression, this fix is just hiding the issue, we must have changed something around chains being overriden during extend or finish chains

[krisselden]

@bekzod can you git bisect to find the regressing commit? this fix is no good, it is just hiding the unbalanced watch/unwatch. This is going to cause other more subtle bugs.

[bekzod]

@krisselden roger that

[bekzod]

found offending commit 0c72faa

[bekzod]

will checkout why it is happening later today