Rename message xml drawable so it's found on ldpi (1/2)

See ag/1010737 for a more detailed explanation.

In this half of the multi-project submit we just
use the new drawable name and remove the
redundant set of pngs (i.e. the same pngs are
also in ContactsCommon)

Bug 27047302

Change-Id: Ib87a91cd7cb9e2462d61161e93c482e299d13f4c