Sync server_external_events v2 to v2.1 Part 2

This syncs commit 5e4a5f0d8c62ca6e94ae6db16e9fbe0428805158 which
was made to the v2 version of os-server-external-events but not
the v2.1 version.

Partially implements blueprint v2-on-v3-api

Change-Id: I458b28b1f3cf161b6d40ce3fd8b3a9c5d090bde7
Merge "Sync server_external_events v2 to v2.1 Part 2"