Switching out the role names to make the test runs unique.

Tests pass

```
$ acctests azurerm TestAccAzureRMRole
=== RUN   TestAccAzureRMRoleDefinition_importBasic
--- PASS: TestAccAzureRMRoleDefinition_importBasic (24.38s)
=== RUN   TestAccAzureRMRoleDefinition_importComplete
--- PASS: TestAccAzureRMRoleDefinition_importComplete (14.14s)
=== RUN   TestAccAzureRMRoleAssignment
=== RUN   TestAccAzureRMRoleAssignment/basic
=== RUN   TestAccAzureRMRoleAssignment/basic/roleName
=== RUN   TestAccAzureRMRoleAssignment/basic/builtin
=== RUN   TestAccAzureRMRoleAssignment/basic/custom
=== RUN   TestAccAzureRMRoleAssignment/basic/emptyName
=== RUN   TestAccAzureRMRoleAssignment/import
=== RUN   TestAccAzureRMRoleAssignment/import/basic
=== RUN   TestAccAzureRMRoleAssignment/import/custom
--- PASS: TestAccAzureRMRoleAssignment (118.70s)
    --- PASS: TestAccAzureRMRoleAssignment/basic (77.01s)
        --- PASS: TestAccAzureRMRoleAssignment/basic/roleName (19.05s)
        --- PASS: TestAccAzureRMRoleAssignment/basic/builtin (17.87s)
        --- PASS: TestAccAzureRMRoleAssignment/basic/custom (22.59s)
        --- PASS: TestAccAzureRMRoleAssignment/basic/emptyName (17.51s)
    --- PASS: TestAccAzureRMRoleAssignment/import (41.69s)
        --- PASS: TestAccAzureRMRoleAssignment/import/basic (21.88s)
        --- PASS: TestAccAzureRMRoleAssignment/import/custom (19.80s)
=== RUN   TestAccAzureRMRoleDefinition_basic
--- PASS: TestAccAzureRMRoleDefinition_basic (14.59s)
=== RUN   TestAccAzureRMRoleDefinition_complete
--- PASS: TestAccAzureRMRoleDefinition_complete (12.99s)
=== RUN   TestAccAzureRMRoleDefinition_update
--- PASS: TestAccAzureRMRoleDefinition_update (22.03s)
PASS
ok  	github.com/terraform-providers/terraform-provider-azurerm/azurerm	206.861s
```

azurerm/resource_arm_role_assignment_test.go

@@ -180,7 +180,7 @@ data "azurerm_subscription" "primary" {}
 data "azurerm_client_config" "test" {}
 
 data "azurerm_builtin_role_definition" "test" {
-  name = "Reader"
+  name = "Monitoring Reader"
 }
 
 resource "azurerm_role_assignment" "test" {
@@ -200,7 +200,7 @@ data "azurerm_client_config" "test" {}
 resource "azurerm_role_assignment" "test" {
   name                 = "%s"
   scope                = "${data.azurerm_subscription.primary.id}"
-  role_definition_name = "Reader"
+  role_definition_name = "Log Analytics Reader"
   principal_id         = "${data.azurerm_client_config.test.service_principal_object_id}"
 }
 `, id)
@@ -213,7 +213,7 @@ data "azurerm_subscription" "primary" {}
 data "azurerm_client_config" "test" {}
 
 data "azurerm_builtin_role_definition" "test" {
-  name = "Reader"
+  name = "Site Recovery Reader"
 }
 
 resource "azurerm_role_assignment" "test" {