core: prevent the cylon when confirmation_spawn=yes (#2194)

core: prevent the cylon when confirmation_spawn=yes (#2194)

When booting with systemd.confirm_spawn=true, the eye of cylon
animation kicks in pretty quickly so user doesn't have any chance to
answer the questions which services to start before the confirmation
message is screwed by the cylon.

This basically breaks the confirm_spawn functionality completely.

This patch prevents the cylon animation to kick in when
confirmation_spawn=yes.

Fixes: #2194