Allow user to set the dnsPolicy field

Currently it was discovered when using builders that the DNSPolicy field gets set to Default.  However in some cluster configurations (FIPS for example) that setting means DNS resolution from within the builder pod does not get set right and resolution lookup for git clone on a repository to be built will fail with "host not found".   This field needs to configurable so one can set it to ClusterFirst to ensure DNS resolution works.

Acceptance Criteria:

• Adding the field `DNS_POLICY: ClusterFirst` to the executor configuration creates a job object with the `dnsPolicy` field set to `ClusterFirst`
• Omitting `DNS_POLICY` defaults the `dnsPolicy` field on the job object to `Default`