tools (datetime, utils): fix incorrect use of naive object: `tools.datetime.format_datetime` was expecting aware datetime objects while `tools.utils.xmpp_date` was returning naive datetime objects. A check has been added to the former one, and latter one has been modified to return aware datetime objects.

#!/bin/sh

eval $(dbus-launch --sh-syntax)

nohup /usr/bin/Xtigervnc -geometry 1024x768 -desktop "Libervia e2e test" -rfbport 5900 -SecurityTypes None :0 &
nohup openbox &
exec libervia-backend fg