fix for leak in account wizard:
E/WindowManager: android.view.WindowLeaked: Activity cx.ring.account.AccountWizard has leaked window (...) that was originally added here
    at android.view.ViewRootImpl.<init>(ViewRootImpl.java:363)
    at android.app.AlertDialog$Builder.show(AlertDialog.java:987)
    at cx.ring.account.AccountWizard$9.run(AccountWizard.java:293)
    at android.os.Handler.handleCallback(Handler.java:739)

Change-Id: I857966cb23fb6df23fd1f3750607397de68637b0