Fix test failure on upgrade_v5_test

[jiangphcn]

Overview

Fix test failure on upgrade_v5_test.

Testing recommendations

make check skip_deps+=couch_epi apps=couch

module 'couch_bt_engine_header'
  couch_bt_engine_header: upgrade_v5_to_v7_test...ok
  couch_bt_engine_header: upgrade_uuid_test...ok
  couch_bt_engine_header: upgrade_epochs_test...ok
  couch_bt_engine_header: get_uuid_from_old_header_test...ok
  couch_bt_engine_header: get_epochs_from_old_header_test...ok
  [done in 0.015 s]

Related Issues or Pull Requests

#1657
COUCHDB-3326

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;