provider/azurerm: fixing a bug refreshing the azurerm_redis_cache

[tombuildsstuff]

Currently, attempting to plan when an azurerm_redis_cache resource has been deleted in the portal - Terraform returns an error:

$ envchain azurerm terraform plan -refresh
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.

azurerm_resource_group.test: Refreshing state... (ID: /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/tharvey-devrg)
azurerm_redis_cache.redis: Refreshing state... (ID: /subscriptions/00000000-0000-0000-0000-...providers/Microsoft.Cache/Redis/redis0)
Error refreshing state: 1 error(s) occurred:

* azurerm_redis_cache.redis: azurerm_redis_cache.redis: Error making Read request on Azure Redis Cache redis0: redis.GroupClient#Get: Failure responding to request: StatusCode=404 -- Original Error: autorest/azure: Service returned an error. Status=404 Code="ResourceNotFound" Message="The Resource 'Microsoft.Cache/Redis/redis0' under resource group 'tharvey-devrg' was not found.

This PR checks for a HTTP Not Found result - and removes it from the state if it doesn't exist:

$ envchain azurerm terraform plan -refresh
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.

azurerm_resource_group.test: Refreshing state... (ID: /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/tharvey-devrg)
azurerm_redis_cache.redis: Refreshing state... (ID: /subscriptions/00000000-0000-0000-0000-...providers/Microsoft.Cache/Redis/redis0)
The Terraform execution plan has been generated and is shown below.
Resources are shown in alphabetical order for quick scanning. Green resources
will be created (or destroyed and then created if an existing resource
exists), yellow resources are being changed in-place, and red resources
will be destroyed. Cyan entries are data sources to be read.

Note: You didn't specify an "-out" parameter to save this plan, so when
"apply" is called, Terraform can't guarantee this is what will execute.

+ azurerm_redis_cache.redis
    capacity:                                 "1"
    enable_non_ssl_port:                      "false"
    family:                                   "C"
    hostname:                                 "<computed>"
    location:                                 "westeurope"
    name:                                     "redis0"
    port:                                     "<computed>"
    primary_access_key:                       "<computed>"
    redis_configuration.#:                    "1"
    redis_configuration.0.maxclients:         "1000"
    redis_configuration.0.maxmemory_delta:    "<computed>"
    redis_configuration.0.maxmemory_policy:   "volatile-lru"
    redis_configuration.0.maxmemory_reserved: "<computed>"
    resource_group_name:                      "tharvey-devrg"
    secondary_access_key:                     "<computed>"
    sku_name:                                 "Standard"
    ssl_port:                                 "<computed>"
    tags.%:                                   "2"
    tags.environment:                         "production"
    tags.role:                                "redis"


Plan: 1 to add, 0 to change, 0 to destroy.

Fixes #13896

[tombuildsstuff]

Tests pass:

[grubernaut]

LGTM, minor nit to add a comment on why delaying the error catch is necessary, but looks good otherwise. 💯

[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 have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.