Add wait_for_instances field to IGM and self_link option to the IG data source (hashicorp#1222)

* Add wait_for_instances field to IGM and self_link option to the IG data source

* don't be clever with errors

Author: danawillow

Diff for: docs/d/google_compute_instance_group.html.markdown

@@ -23,15 +23,16 @@ data "google_compute_instance_group" "all" {
 
 The following arguments are supported:
 
-* `name` - (Required) The name of the instance group.
-
-* `zone` - (Required) The zone of the instance group.
-
-- - -
+* `name` - (Optional) The name of the instance group. Either `name` or `self_link` must be provided.
 
 * `project` - (Optional) The ID of the project in which the resource belongs. If it
     is not provided, the provider project is used.
 
+* `self_link` - (Optional) The self link of the instance group. Either `name` or `self_link` must be provided.
+
+* `zone` - (Optional) The zone of the instance group. If referencing the instance group by name
+    and `zone` is not provided, the provider zone is used.
+
 ## Attributes Reference
 
 The following arguments are exported:

Diff for: docs/r/compute_instance_group_manager.html.markdown

@@ -101,6 +101,10 @@ The following arguments are supported:
     instances in the group are added. Updating the target pools attribute does
     not affect existing instances.
 
+* `wait_for_instances` - (Optional) Whether to wait for all instances to be created/updated before
+    returning. Note that if this is set to true and the operation does not succeed, Terraform will
+    continue trying until it times out.
+
 ---
 
 * `auto_healing_policies` - (Optional, [Beta](/docs/providers/google/index.html#beta-features)) The autohealing policies for this managed instance

Diff for: docs/r/compute_region_instance_group_manager.html.markdown

@@ -95,6 +95,10 @@ The following arguments are supported:
     instances in the group are added. Updating the target pools attribute does
     not affect existing instances.
 
+* `wait_for_instances` - (Optional) Whether to wait for all instances to be created/updated before
+    returning. Note that if this is set to true and the operation does not succeed, Terraform will
+    continue trying until it times out.
+
 ---
 
 * `auto_healing_policies` - (Optional, [Beta](/docs/providers/google/index.html#beta-features)) The autohealing policies for this managed instance