Bug 570354 - Switch MirrorApplication to use ArtifactChecksumComparator

Still uses MD5 checksums but uses the code used in the rest of the
codebase.
MD5ArtifactComparator is deprecated and this is step towards switching
it to support SHA-256.

Change-Id: Ie53607a8956e17312aaa1aee2e0a7d84bc7089d3
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>
3 files changed