Fix FIPS job - nslookup_target

This patch sets a zuul variable "nslookup_target" to 'opendev.org'
to fix the FIPS jobs.

The nslookup_target var was added as a required var for the enable-fips
role in [1].

[1] https://opendev.org/zuul/zuul-jobs/commit/25caf7ef5e5801892ed575b063824ffb8355fb1e

Change-Id: Ifb0f929cf7cb9dddedcf4f0bd930b4bd7ca2dd72
1 file changed