(QENG-1231) add onpass option to --preserve-hosts
* add spec tests similar to onfail spec tests
* add cleanup to rescue when --preserve-hosts onpass
* add help statement for onpass
remove non-capture from regex groups
Merge pull request #475 from er0ck/feature/master/QENG-1231-preserve_hosts_onpass

(QENG-1231) add onpass option to --preserve-hosts