Add reviewers from OWNERS all at once

Make a single invocation to the add reviewer action to a change
for all the OWNERS that have to be assigned automatically.

This avoids the spamming of the reviewers with multiple notifications,
one per additional reviewer.

Change-Id: I615e55d1f6c574016643be4820e2eb71e4c3643c
diff --git a/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java b/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java
index 70c3e67..3335144 100644
--- a/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java
+++ b/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java
@@ -86,8 +86,8 @@
                 account,
                 changeInfo._number);
           }
-          gApi.changes().id(changeInfo.id).current().review(in);
         }
+        gApi.changes().id(changeInfo.id).current().review(in);
       }
     } catch (RestApiException | OrmException e) {
       log.error("Couldn't add reviewers to the change", e);