Creating ns1_user with security_manage_global_2fa true even if set to false

[ThiagoYU]

Terraform set default value to false, but in some cases p.Security was not initialized, so the struct sent in the request didn't have the p.Security default values, so it was using the API default value, which is true.

Even if setting security_manage_global_2fa = false, because GetOk returns false if the value is equal to Zero-value, how Bool zero value is false, it never sets security_manage_global_2fa = false.
The change forces the p.Security to be initialized if it wasn't and change the permission to true if the parameter is passed.

[pcatalini]

LGTM

[Zach-Johnson]

This looks good to me, tested it locally and it looks to be working. Let's add or modify a test case for this in resource_user_test.go please

[Zach-Johnson]

lgtm, nice!