Update git submodules

* Update plugins/hooks from branch 'master'
  - Rework ref-update hook to use RefOperationValidationListener
    
    Instead of being invoked on every commit received, the ref-update hook
    is now invoked before the ref update operation is finalized. Note that
    the hook is no longer invoked on commits pushed for review or on changes
    that are merged. It is invoked for creation/deletion of refs, and for
    ref updates caused by direct pushes (i.e. bypassing review).
    
    The previous behavior of the ref-update hook is moved into a new hook
    named commit-received. A new parameter '--cmdref' is added, and the
    special handling of 'refs/for' and 'refs/changes' is removed.
    
    Also-By: David Pursehouse <dpursehouse@collab.net>
    Bug: Issue 5739
    Change-Id: I24d8580aef463f8bfb078d90a4e9e2ce6e8b9b93
    
diff --git a/plugins/hooks b/plugins/hooks
index a329746..60adf57 160000
--- a/plugins/hooks
+++ b/plugins/hooks
@@ -1 +1 @@
-Subproject commit a32974634954aa904acc00644bb0beb58b1ea934
+Subproject commit 60adf5742f44badc5193b42ffc841bb2d0f6e442