INTMDB-269: Fix issue with default auto_scaling_disk_gb_enabled value

[abner-dou]

Description

Please include a summary of the fix/feature/change, including any relevant motivation and context.

Link to any related issue(s):INTMDB-269

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 RESULT:

--- PASS: TestAccResourceMongoDBAtlasCluster_tenant (1558.34s)
PASS
coverage: 6.8% of statements
ok github.com/mongodb/terraform-provider-mongodbatlas/mongodbatlas 1560.775s coverage: 6.8% of statements
? github.com/mongodb/terraform-provider-mongodbatlas/version [no test files]

[thetonymaster]

Talk with @coderGo93 about adding some tests with this, since those tests might need to be added with terratest

[andreaangiolillo]

Please, make sure that all the tests are passing before asking for a review. Thanks!
Changes LGTM.

[themantissa]

LGTM

[andreaangiolillo]

LGTM

[thetonymaster]

LGTM, can you just squash the fix commits, since just a fix message is annoying