Fix some issues with updating fields for several resources

[lawliet89]

This is a follow up to several PRs I made recently:

Fix incorrect field updating in gcp_auth_backend_role

I made a mistake in setting the new TypeBool fields.

GetOk will return whether or not the key has been set to a non-zero value at some point as the second value. If the value is false, the second parameter will be false. Thus if a field was changed from true to false, this will never be caught.

Fix d.Set

When using d.Set on aggregate types, they can potentially fail. See Terraform docs.

I've updated some resources to check for these:

• gcp_auth_backend_role
• kubernetes_auth_backend_role
• identity_group

[tyrannosaurus-becks]

Thanks @lawliet89!