Fix fallthrough param for coredns to avoid coredns misconfiguration

In cases with externaldns deployed and cluster domain contains _
the CoreDNS may start working unexpected. This change introducing
force replacing of _ to - in externaldns and CoreDNS config maps.

Change-Id: I058d2bb4023d05c0a5552a0fb8c5a2bd0451d1e2
Related-PROD: PROD-25505
2 files changed