Doesn't properly handle cases when same domain has multiple challenges

[mesudip]

Request [200] : GET https://acme-staging-v02.api.letsencrypt.org/directory step=Fetch Acme Directory
Request [204] : GET https://acme-staging-v02.api.letsencrypt.org/acme/new-nonce step=Acme request:newAccount > Fetch new Nonce
Request [201] : POST https://acme-staging-v02.api.letsencrypt.org/acme/new-acct step=Acme request:newAccount
New Acme Account registered
Request [201] : POST https://acme-staging-v02.api.letsencrypt.org/acme/new-order step=Acme request:newOrder
Request [200] : GET https://acme-staging-v02.api.letsencrypt.org/acme/authz/257271363/21146544003 step=Get Challenge [*.admin.example.com]
Request [200] : GET https://acme-staging-v02.api.letsencrypt.org/acme/authz/257271363/21146544013 step=Get Challenge [*.app.example.com]
Request [200] : GET https://acme-staging-v02.api.letsencrypt.org/acme/authz/257271363/21146544023 step=Get Challenge [admin.example.com]
Request [200] : GET https://acme-staging-v02.api.letsencrypt.org/acme/authz/257271363/21146544033 step=Get Challenge [app.example.com]
CloudflareChallengeSolver [ admin.example.com ]: Added Record _acme-challenge.admin.example.com
CloudflareChallengeSolver [ app.example.com ]: Added Record _acme-challenge.app.example.com
CloudflareChallengeSolver [ admin.example.com ]: Added Record _acme-challenge.admin.example.com
CloudflareChallengeSolver [ app.example.com ]: Added Record _acme-challenge.app.example.com
Waiting 20 seconds for DNS propagation .. 
Request [200] : POST https://acme-staging-v02.api.letsencrypt.org/acme/chall/257271363/21146544003/3MO5Lw step=Verify Challenge [admin.example.com]
Request [200] : POST https://acme-staging-v02.api.letsencrypt.org/acme/chall/257271363/21146544013/Iph8Kw step=Verify Challenge [app.example.com]
Request [200] : POST https://acme-staging-v02.api.letsencrypt.org/acme/chall/257271363/21146544023/i7qCAQ step=Verify Challenge [admin.example.com]
Request [200] : POST https://acme-staging-v02.api.letsencrypt.org/acme/chall/257271363/21146544033/CfpOow step=Verify Challenge [app.example.com]
Request [200] : POST https://acme-staging-v02.api.letsencrypt.org/acme/authz/257271363/21146544003 step=Query Challenge Status [admin.example.com]
Request [200] : POST https://acme-staging-v02.api.letsencrypt.org/acme/authz/257271363/21146544013 step=Query Challenge Status [app.example.com]
An error occurred: {
  "name": "AcmeInvaliOrderError",
  "message": "_acme-challenge.app.example.com doesn't have a valid DNS record",
  "step": "Query Challenge Status",
  "detail": {
    "url": "https://acme-staging-v02.api.letsencrypt.org/acme/chall/257271363/21146544013/Iph8Kw",
    "dns": {
      "error": "DNS record doesn't exist"
    },
    "hostname": "_acme-challenge.app.example.com"
  }
}