[util] flag to specify hosts to fail DNS resolution

This patch adds a flag to specify the specific hostports to which
failures are injected by --fail_dns_resolution. I intend on using this
in a subsequent patch.

Change-Id: I25f2d3073fa0fa0a430afacf7c8cd1402e6bd6ab
Reviewed-on: http://gerrit.cloudera.org:8080/17584
Reviewed-by: Alexey Serbin <aserbin@cloudera.com>
Tested-by: Andrew Wong <awong@cloudera.com>
2 files changed