plugin/file: add TXT RR test case (#5079)
plugin/file: add TXT RR test case (#5079)

Signed-off-by: xuweiwei <1688ab3585f7cf4dca883afdf8a25a7a4169187f@cmss.chinamobile.com>
coredns/coredns,chrisohaver/coredns,yongtang/coredns