[HSS] Add hss_event_init after change to event system

[jmasterfunk84]

When use_mongodb_change_stream is enabled, the HSS is unable to start due to the following error:

[app] FATAL: hss_event_new: Assertion `e' failed. (../src/hss/hss-event.c:46)

In #2739, the event functions were moved into the hss app, however, hss_event_init is never called. This adds the call to the function to allow the hss to start with change streams enabled.

[acetcom]

@jmasterfunk84

Please ensure that the 'hss_event_final()' function is invoked within the 'hss_terminate()' function in the 'hss-init.c' file.

Thanks a lot!
Sukchan

[jmasterfunk84]

@acetcom

Thanks, I've made that change, too!