Fix contact picture color generation.

Make sure to return different colors for senders with different name,
but the same mail address (e.g. mails sent by certain issue tracking
systems).

src/com/fsck/k9/activity/misc/ContactPictureLoader.java

@@ -161,7 +161,7 @@ public class ContactPictureLoader {
             return mDefaultBackgroundColor;
         }
 
-        int val = address.getAddress().toLowerCase(Locale.getDefault()).hashCode();
+        int val = address.hashCode();
         int rgb = CONTACT_DUMMY_COLORS_ARGB[Math.abs(val) % CONTACT_DUMMY_COLORS_ARGB.length];
         return rgb;
     }