nscd: does not warn about invalid values what parsing config file

PR: 202135
Submitted by: amutu@amutu.com
Reported By: Trond.Endrestol@ximalas.info
Reviewed by: markj, freqlabs
MFC after: 4 weeks
Sponsored by: Klara Inc.
Event: July 2020 Bugathon
Differential Revision: https://reviews.freebsd.org/D25627