xds: Priority policy restarts timer on CONNECTING->CONNECTING transition

[dfawley]

If the priority policy's timer for a child (the init timer) expires -- started here:

grpc-go/xds/internal/balancer/priority/balancer_child.go

Line 105 in 0ebea3e

cb.startInitTimer()

If the child is still CONNECTING and then it produces a new CONNECTING picker, this code will restart it:

grpc-go/xds/internal/balancer/priority/balancer_priority.go

Line 201 in 0ebea3e

case connectivity.Connecting:

This should be able to be fixed by checking if the old state was also CONNECTING, and avoiding starting the timer if so.