core: Entity ID is not set or invalid

The Exchanging Device and Mailbox States could not working
if the Entity ID (EID) is not set manually and can't be obtained
from ethernet interface.

This patch replaces debug message to warning
and addes missing description about option 'entityid' to
asterisk.conf.sample.

With this patch the asterisk also:
(1) decline loading the modules which won't work without EID:
    res_corosync and res_pjsip_publish_asterisk.
(2) warn if EID is empty on loading next modules:
    pbx_dundi, res_xmpp

Starting with v197 systemd/udev will automatically assign "predictable"
names for all local Ethernet interfaces.
This patch also addes some new ethernet prefixes "eno" and "ens".

ASTERISK-26164 #close

Change-Id: I72d712f1ad5b6f64571bb179c5cb12461e7c58c6