[services] Fix reactors - Initialize status holders

Summary:
Depends on D4013

I forgot to initialize statusHolders and it resulted in crashes

Test Plan: Run services and use grpc playground to make any call to the backup server - it crashed before but with this change it doesn't.

Reviewers: palys-swm, ashoat

Reviewed By: ashoat

Subscribers: ashoat, palys-swm, Adrian, atul, yayabosh

Differential Revision: https://phabricator.ashoat.com/D4026