Leader election delays vulndb import and prevents getting results in freshly installed instance

Currently, the leader election is default initialised with not the leader:

⇨ http server started on [::]:8080
10:35AM INF daemons/providers.go:201 not the leader - skipping background jobs
10:40AM INF daemons/providers.go:201 not the leader - skipping background jobs

This leads to a 10-minute delay of the vulndb import. When having a fresh install the users want to get results fast. Especially when using the docker install/ try out way. When freshly started the devguard api instance should instantly try to claim leadership. If not gained, skip background jobs. When gaining leader role, start vulndb import immediately.

⇨ http server started on [::]:8080
10:35AM INF daemons/providers.go:201 not the leader - skipping background jobs
10:40AM INF daemons/providers.go:201 not the leader - skipping background jobs
...
10:45AM INF daemons/vulndb_daemon.go:17 updating vulndb
10:45AM INF vulndb/vulndb_service.go:478 start vulndb import processing=streaming limitedToTables=[]