Avoid creation of document if deleting attachment on non-existent doc

[jiangphcn]

Overview

Prior to the change in this PR, one new document was unexpectedly created after a request is issued to delete attachment on non-existent document. This PR is aimed to address this to return 404 (Not Found) instead of creating new document.

Testing recommendations

The newly introduced test case should_return_404_for_delete_att_on_notadoc covers the steps to test the change in this PR. In addition, two additional test cases should_return_409_for_del_att_without_rev and should_return_200_for_del_att_with_rev are introduced to make sure that there is no regression.

======================== EUnit ========================
chttpd db tests
  chttpd_db_test:71: should_return_ok_true_on_bulk_update...[0.107 s] ok
  chttpd_db_test:86: should_accept_live_as_an_alias_for_continuous...[0.054 s] ok
  chttpd_db_test:107: should_return_404_for_delete_att_on_notadoc...[0.005 s] ok
  chttpd_db_test:129: should_return_409_for_del_att_without_rev...[0.052 s] ok
  chttpd_db_test:155: should_return_200_for_del_att_with_rev...[0.078 s] ok
[os_mon] cpu supervisor port (cpu_sup): Erlang has closed
  [done in 1.563 s]

JIRA issue number

COUCHDB-3362

Related Pull Requests

N/A

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• [] Documentation reflects the changes;
• I will not forget to update rebar.config.script
  with the correct commit hash once this PR get merged.

No documentation change since the changed behavior is aligned with statement in document http:https://docs.couchdb.org/en/2.0.0/api/document/attachments.html#delete--db-docid-attname

[iilyak]

Tests pass locally

    Running test function(s):
      chttpd_db_doc_size_tests:all_test_/0
      chttpd_db_test:all_test_/0
======================== EUnit ========================
chttpd db tests
  chttpd_db_test:71: should_return_ok_true_on_bulk_update...[0.091 s] ok
  chttpd_db_test:86: should_accept_live_as_an_alias_for_continuous...[0.032 s] ok
  chttpd_db_test:107: should_return_404_for_delete_att_on_notadoc...[0.016 s] ok
  chttpd_db_test:129: should_return_409_for_del_att_without_rev...[0.027 s] ok
  chttpd_db_test:155: should_return_200_for_del_att_with_rev...[0.038 s] ok
  [done in 0.808 s]
chttpd db max_document_size tests
  chttpd_db_doc_size_tests:72: post_single_doc...[0.002 s] ok
  chttpd_db_doc_size_tests:83: put_single_doc...[0.001 s] ok
  chttpd_db_doc_size_tests:100: bulk_doc...ok
  chttpd_db_doc_size_tests:128: put_post_doc_attach_inline...ok
  chttpd_db_doc_size_tests:149: put_multi_part_related...ok
  chttpd_db_doc_size_tests:172: post_multi_part_form...ok
  [done in 0.596 s]
=======================================================
  All 11 tests passed.