Back out the Set changes from #1217.

PR #1217 mistakenly updated the Set logic when flattening backends,
which caused some cascading errors and wasn't strictly necessary to
resolve the issue at hand. This backs out those changes, and instead
makes the smallest possible change to resolve the initial error, by
separating the logic for flattening regional backends from the logic for
flattening global backends.

google/resource_compute_backend_service.go

@@ -417,8 +417,8 @@ func expandBackends(configured []interface{}) ([]*compute.Backend, error) {
 	return backends, nil
 }
 
-func flattenBackends(backends []*compute.Backend) *schema.Set {
-	result := make([]interface{}, 0, len(backends))
+func flattenBackends(backends []*compute.Backend) []map[string]interface{} {
+	result := make([]map[string]interface{}, 0, len(backends))
 
 	for _, b := range backends {
 		data := make(map[string]interface{})
@@ -433,7 +433,7 @@ func flattenBackends(backends []*compute.Backend) *schema.Set {
 		result = append(result, data)
 	}
 
-	return schema.NewSet(resourceGoogleComputeBackendServiceBackendHash, result)
+	return result
 }
 
 func expandBackendService(d *schema.ResourceData) (*compute.BackendService, error) {

google/resource_compute_region_backend_service.go

@@ -339,8 +339,8 @@ func resourceGoogleComputeRegionBackendServiceBackendHash(v interface{}) int {
 	return hashcode.String(buf.String())
 }
 
-func flattenRegionBackends(backends []*compute.Backend) *schema.Set {
-	result := make([]interface{}, 0, len(backends))
+func flattenRegionBackends(backends []*compute.Backend) []map[string]interface{} {
+	result := make([]map[string]interface{}, 0, len(backends))
 
 	for _, b := range backends {
 		data := make(map[string]interface{})
@@ -350,5 +350,5 @@ func flattenRegionBackends(backends []*compute.Backend) *schema.Set {
 		result = append(result, data)
 	}
 
-	return schema.NewSet(resourceGoogleComputeRegionBackendServiceBackendHash, result)
+	return result
 }