ContactList: Separate creation of ContactListAdapter and managment of the
group list
This is two separate things. getContactListAdapter is called in
ContactListFragment.onActivityCreated() which is during a fragment
transaction.
Management of the group list calls FragmentPagerAdapter.notifyDataSetChanged()
which repopulate the FragmentPagerAdapter and to do so calls
FragmentManager.executePendingTransactions() in a recursive way and is not
allowed (IllegalStateException).