Trim fedora mirror

The fedora mirror is our largest mirror (850GB about twice as big as the
next mirror). Much of this size is due to the fedora atomic images we
mirror.

On further investigation I notice that we are mirroring ppc images (for
which we do not have cpus to run them on), image for fedora 25 and 36
which are quite EOL'd, and our exclusion of the raw.xz and vagrant
images is failing.

Update the rsync excludes to ensure we don't mirror any of these images
we don't need.

Change-Id: I86856cb4e51b0e687aac45a1f014f87c5141318f

playbooks/roles/mirror-update/files/fedora-mirror-update

@@ -91,8 +91,11 @@ $K5START rsync -rltDvz \
     --delete-excluded \
     --exclude="testing/" \
     --exclude="Atomic/" \
-    --exclude="CloudImages/x86_64/images/*.raw.xz" \
-    --exclude="CloudImages/x86_64/images/*.box" \
+    --exclude="Fedora-Atomic-25-*/" \
+    --exclude="Fedora-Atomic-26-*/" \
+    --exclude="ppc64le/" \
+    --exclude="images/*.raw.xz" \
+    --exclude="images/*.box" \
     $MIRROR/ $BASE/atomic/
 
 # TODO(pabelanger): Validate rsync process