Use a valid :tag for default-registry (was breaking reflection)

Bug was introduced in 2ea88520dea284f3f5ca5395fb8a30f0db9e7fb0
(cherry picked from commit 0104f32d1e41a9e2092b5fcad6dff658d1755750)
Update changelog
Merge pull request #42 from timmc/def-reg-tag-backport-2.1.x

Backporting 0104f32d (default-registry :tag) to stable branch