make TabletExternallyReparented more robust#5151

Merged

deepthi merged 8 commits intovitessio:masterfrom

planetscale:ds-reparent

Sep 13, 2019

Commits on Sep 9, 2019

along with old master also update any other tablet that thinks it is master to REPLICA
deepthi
committed

Commits on Sep 10, 2019

Commits on Sep 11, 2019

make TER idempotent so that it can be called again if the first call does not complete all steps
deepthi
committed

Commits on Sep 12, 2019

add comments explaining why some synchronization has been removed
deepthi
committed
fix/add descriptive comments, avoid unnecessary topo calls, merge 2 loops into 1 and remove use of channel that is no longer needed
deepthi
committed

Commits on Sep 13, 2019

defer event update, only make a copy of tablet if we are changing it, use one tmc for all calls to RefreshState
deepthi
committed