CallDetailActivity: Don't offer to add a number to contacts.

This is related to barrykn/android-cm7-bkndh1#9, and it's a
manual backport of:

commit f393e5a76f0633d81e34e9c0b93de80dea675ce7
Author: Barry K. Nathan <barryn@pobox.com>
Date:   Sun Jun 2 08:45:21 2013 -0700

    CallDetailHeader: Don't offer to add a number to contacts.

    This is related to barrykn/android-cm7-bkndh1#9.