Chan address in addressbook minor issues #878

Reported over BM

1. There is two chans: 2cW67GEKkHGonXKZLCzouLLxnLym3azS8r and
   2DAV89w336ovy6BUJnfVRD5B9qipFbRgmr with name "general".
2. When connected I knew only one of it thought
   2DAV89w336ovy6BUJnfVRD5B9qipFbRgmr was a person with his own name,
   say "John Doe".
3. I've added 2DAV89w336ovy6BUJnfVRD5B9qipFbRgmr to the address
   book.
4. Then some guy posted list of chans and I've added
   2DAV89w336ovy6BUJnfVRD5B9qipFbRgmr to a chans list.
5. Then figured out it wasn't a person and tried to delete it from
   an address book or rename
6. After restarting Bitmessage it was restoring in the address book
7. Deleted from addressbook deleted from chans, added to chans,
   problem has gone.

So basically if an address is both in the addressbook and in chan, you can't delete it from the addressbook.