[mdns] remove package_name parameter from package targets

This CL removes all the package_name parameters from package targets
relating to mdns. It also removes the superfluous package file
package/prod/mdns_util, which is leftover from renaming mdns_util to
mdns-util.

TEST: no behavior change, booted to ensure mdns still runs
Change-Id: I23193c62a007a0dc35d128f5b78afbe55f5d1b5e
7 files changed