adapt init-wait for srlinux containers

[hellt]

srlinux containers use a named dataplane interfaces

eX-Y - where

• X - linecard number
• Y - port number

this change makes init-wait to sense those interfaces

Output from the init-wait container of a srlinux pod

/ # ls -1v /sys/class/net/ | grep 'eth\|ens\|eno\|^e[0-9]'
eth0
e1-1
e1-2