packaging: setup: Display a note for db credentials

Allow making getCredentials display a note prior to asking for
credentials.

Change-Id: I4053b5426b1fcb64fda2697ad4310f4044b13d98
Bug-Url: https://bugzilla.redhat.com/1159789
Bug-Url: https://bugzilla.redhat.com/1162549
Signed-off-by: Yedidyah Bar David <didi@redhat.com>