fix: error when scaling elasticache_replication_group

[blgm]

Description

When scaling a aws_elasticache_replication_group up or down (via num_cache_clusters), if AWS runs a snapshot during during the operation, the update will fail with error unexpected state 'snapshotting', wanted target 'available':

Error: modifying ElastiCache Replication Group (csbb2a2560a-acf7-4106-9618-4263082cb536) clusters: error waiting for ElastiCache Replication Group (csbb2a2560a-acf7-4106-9618-4263082cb536) replica addition: unexpected state 'snapshotting', wanted target 'available'.
              last error: %!s(<nil>) with aws_elasticache_replication_group.redis, on main.tf line 46, in resource "aws_elasticache_replication_group" "redis": 46: resource "aws_elasticache_replication_group" "redis"

Suggestion is that as "snapshotting" is an allowed state in the WaitReplicationGroupAvailable() function, for consistency it makes sense for it to also be allowed in the WaitReplicationGroupMemberClustersAvailable() function that gets called when scaling the replication group.

Relations

None

References

None

Output from Acceptance Testing

$ make testacc TESTS='TestAccElastiCacheReplicationGroup_' PKG=elasticache ACCTEST_PARALLELISM=5
...

I wasn't able to get this to run successfully, but for reasons relating to VPC constraints rather than anything likely to relate to the change.

[github-actions]

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[github-actions]

Welcome @blgm 👋

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[github-actions]

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