Revisit locking retry/back-off

[vrivellino]

Exclusive locking is implemented via step functions' retry semantics:

spoptimize/sam.yml

Lines 322 to 326 in 4aa555c

	"Retry": [{
	"ErrorEquals": [ "GroupLocked" ],
	"IntervalSeconds": 5,
	"MaxAttempts": 20,
	"BackoffRate": 1.5

I'm not sure this is the right long-term solution. For larger autoscaling groups, it may take hours for all instances to be replaced after a deploy or mass update.

Perhaps allow for more than one instance to be replaced my Spoptimize (configurable via tag)? Or just have a static interval between retries?