Make route priority optional, default to 1000

Fixes hashicorp#1009

Author: jphalip

google/resource_compute_route.go

@@ -39,8 +39,9 @@ func resourceComputeRoute() *schema.Resource {
 
 			"priority": &schema.Schema{
 				Type:     schema.TypeInt,
-				Required: true,
+				Optional: true,
 				ForceNew: true,
+				Default:  1000,
 			},
 
 			"next_hop_gateway": &schema.Schema{

google/resource_compute_route_test.go

@@ -153,7 +153,6 @@ resource "google_compute_route" "foobar" {
 	dest_range = "15.0.0.0/24"
 	network = "${google_compute_network.foobar.name}"
 	next_hop_ip = "10.0.1.5"
-	priority = 100
 }`, acctest.RandString(10), acctest.RandString(10))
 }