Sign out the account's other sessions when its password changes

Changing the password is how someone shuts out whoever else is signed
in to their account, but every session opened with the old password
stayed valid. Now the others end and their live connections close, as
on sign-out. The session the password was changed from stays signed in.

Changing the password outside a request, as from a console, ends every
session.

From #371. 1.5.2 has no record snapshot or response cache, so the test
that a cached session lookup doesn't outlive the password change is
left out; the rest applies as it is.

(cherry picked from commit c78c3fd7ef)

app/controllers/users/profiles_controller.rb

@@ -8,6 +8,8 @@ class Users::ProfilesController < ApplicationController
 
   def update
     @user.update user_params
+    disconnect_remote_connections if @user.saved_change_to_password_digest?
+
     redirect_to user_profile_url, notice: update_notice
   end