Process user deactivation

[xcoulon]

User deactivation will be performed on a regular basis, calling the appropriate endpoint on fabric8-auth (see fabric8-services/fabric8-auth#780).

In order to avoid running a separate batch on the platform, we could use a go routine built in the admin console service itself (with a lock on a table to avoid concurrent accesses if we run multiple pods).

The deactivation process is the following:

1. call fabric8-auth to retrieve a list of users to deactivate (limited to a certain number of accounts) using
2. call fabric8-auth to deactivate each account and record an "audit log" of each user deactivation
3. goto 1 until the list of users to deactivate is empty