Close live connections from the model on any password change

The sessions end wherever the password changes, but only the profile
page closed the live connections, so a change from a console left a
signed-out device receiving messages until it dropped. Close them after
commit from User, logging rather than failing if the realtime service
can't be reached, since the password is saved by then.

From #371.

(cherry picked from commit c6e0105491)

test/models/user_test.rb

@@ -50,6 +50,14 @@ class UserTest < ActiveSupport::TestCase
     end
   end
 
+  test "changing the password outside a request closes the account's live connections" do
+    remote_connections = mock
+    remote_connections.expects(:disconnect).with(reconnect: true)
+    ActionCable.server.stubs(:remote_connections).returns(mock.tap { |m| m.expects(:where).with(current_user: users(:david)).returns(remote_connections) })
+
+    users(:david).update!(password: "a new secret123456")
+  end
+
   test "changing the password keeps the session it was changed from" do
     Current.session = users(:david).sessions.start!(user_agent: "This device", ip_address: "127.0.0.1")
 
@@ -59,6 +67,8 @@ class UserTest < ActiveSupport::TestCase
   end
 
   test "changing other details keeps every session" do
+    ActionCable.server.expects(:remote_connections).never
+
     assert_no_changes -> { users(:david).sessions.count } do
       users(:david).update!(name: "Dave", email_address: "dave@37signals.com")
     end