core: log check is user admin in debug

Log the check "if user is an admin" as debug and not info.
This check is done every 1 minute for logged in users,
thus the log is filled with those messages in info level.

Change-Id: I3f6e7f1ceec4b6d4935035f857281231bacc44e9
Signed-off-by: Alissa Bonas <abonas@redhat.com>