INTMDB-254: Fix replication_specs behaviour when update cluster

[abner-dou]

Description

A validation was re-coded in replication_specs cluster to get the original id when update the cluster

Link to any related issue(s):INTMDB-254

Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the Terraform contribution guidelines
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code

Further comments

TEST:

--- PASS: TestAccResourceMongoDBAtlasCluster_MultiRegion (1572.79s)
PASS
coverage: 8.1% of statements
ok github.com/mongodb/terraform-provider-mongodbatlas/mongodbatlas 1575.224s coverage: 8.1% of statements
? github.com/mongodb/terraform-provider-mongodbatlas/version [no test files]

[themantissa]

LGTM, thank you for knocking this out quickly (also tests haven't passed yet but will check again before merge - still two approvers to go)

[andreaangiolillo]

LGTM

[thetonymaster]

LGTM