plugin/rewrite: copy msg before rewritting (#4443)
plugin/rewrite: copy msg before rewritting (#4443)

Copy the msg to prevent messing with the (via the pointer) original
created message that may be stored in the cache or anything other data
store.

Signed-off-by: Miek Gieben <00b357f94cf3a1145a32703fb42e2d80418ab806@miek.nl>
miekg/coredns,yongtang/coredns,coredns/coredns,miekg/coredns,chrisohaver/coredns