Use API version 2020-03-01 for Loadbalancer

[marc-sensenich]

Closes #7691 by using the 2020-03-01 network API version. Based off a comment by @tombuildsstuff from #7741 as this issue is present on more than just azurerm_lb_rule deletion

The reason for that issue is that service can't tolerate the client sending properties.backendAddressPools.n.properties.backendIPConfigurations in request body for load balancer resource since 2020-05-01, as it is a READ-ONLY attribute (this only occurs when azurerm_lb's sku is Standard).
Currently, Azure Go SDK can trim the READ-ONLY attributes during marshaling, but only for the root level attributes, so, in this case, Go SDK will still marshal the attribute into the request body. This is tracked in issue: Azure/autorest.go#438.

Acceptance Tests

--- PASS: TestAccAzureRMLoadBalancer_standard (74.84s)
--- PASS: TestAccAzureRMLoadBalancer_requiresImport (126.75s)
--- PASS: TestAccAzureRMLoadBalancerRule_disappears (136.04s)
--- PASS: TestAccAzureRMLoadBalancerBackEndAddressPool_basic (140.11s)
--- PASS: TestAccAzureRMLoadBalancerRule_updateMultipleRules (211.43s)
--- PASS: TestAccAzureRMLoadBalancerRule_removal (211.44s)
--- PASS: TestAccAzureRMLoadBalancer_basic (136.61s)
--- PASS: TestAccAzureRMLoadBalancerRule_inconsistentReads (211.45s)
--- PASS: TestAccAzureRMLoadBalancerProbe_basic (321.01s)
--- PASS: TestAccAzureRMLoadBalancer_frontEndConfigPublicIPPrefix (132.72s)
--- PASS: TestAccAzureRMLoadBalancerRule_complete (147.61s)
--- PASS: TestAccAzureRMLoadBalancerProbe_update (341.34s)
--- PASS: TestAccAzureRMLoadBalancerRule_basic (137.91s)
--- PASS: TestAccAzureRMLoadBalancerProbe_requiresImport (169.84s)
--- PASS: TestAccAzureRMLoadBalancerProbe_disappears (392.64s)
--- PASS: TestAccAzureRMLoadBalancerProbe_removal (202.78s)
--- PASS: TestAccAzureRMLoadBalancerProbe_updateProtocol (389.76s)
--- PASS: TestAccAzureRMLoadBalancerRule_update (1464.92s)
--- PASS: TestAccAzureRMLoadBalancerNatPool_removal (1194.92s)
--- PASS: TestAccAzureRMLoadBalancerRule_requiresImport (1464.96s)
--- PASS: TestAccAzureRMLoadBalancer_privateIP (1179.42s)
--- PASS: TestAccAzureRMLoadBalancer_emptyPrivateIP (1157.00s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_basic (1152.61s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_complete (1162.42s)
--- PASS: TestAccAzureRMLoadBalancer_tags (1196.95s)
--- PASS: TestAccAzureRMLoadBalancerOutboundRule_disappears (94.63s)
--- PASS: TestAccAzureRMLoadBalancerOutboundRule_requiresImport (105.37s)
--- PASS: TestAccAzureRMLoadBalancerNatPool_requiresImport (145.97s)
--- PASS: TestAccAzureRMLoadBalancerNatPool_disappears (149.86s)
--- PASS: TestAccAzureRMLoadBalancerBackEndAddressPool_disappears (156.94s)
--- PASS: TestAccAzureRMLoadBalancerNatPool_update (173.39s)
--- PASS: TestAccAzureRMLoadBalancer_frontEndConfig (213.04s)
--- PASS: TestAccAzureRMLoadBalancerOutboundRule_basic (119.46s)
--- PASS: TestAccAzureRMLoadBalancerNatPool_basic (137.47s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_update (192.43s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_disappears (137.54s)
--- PASS: TestAccAzureRMLoadBalancerOutboundRule_update (118.24s)
--- PASS: TestAccAzureRMLoadBalancerOutboundRule_withPublicIPPrefix (164.61s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_updateMultipleRules (193.30s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_removal (171.90s)
--- PASS: TestAccAzureRMLoadBalancerNatRule_requiresImport (180.32s)
--- PASS: TestAccAzureRMLoadBalancerOutboundRule_removal (201.86s)
--- PASS: TestAccAzureRMLoadBalancerBackEndAddressPool_requiresImport (181.10s)
--- PASS: TestAccAzureRMLoadBalancerBackEndAddressPool_removal (226.18s)

[hbuckle]

Can someone please review this? Load balancers have been broken for more than a month now

[marc-sensenich]

@magodo is this one on your radar based on our Slack conversation?

[magodo]

@marc-sensenich Yes, I have looked through this PR and it LGTM, thanks 👍

While downgrading API version needs some thoughts and tests, I am discussing with other maintainers for their opinions on this PR. In the meanwhile, we have some fix in the new Go SDK for the LB issue and trying hard to integrate into terraform azurerm provider.

[tombuildsstuff]

LGTM - thanks for this / apologies for the delay here @marc-sensenich

[tombuildsstuff]

Tests pass:

[ghost]

This has been released in version 2.24.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
    version = "~> 2.24.0"
}
# ... other configuration ...

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 hashibot-feedback@hashicorp.com. Thanks!