Handle DRP installation errors gracefully

[bo-quan]

The current installer does not handle unhappy paths gracefully, e.g.,

TASK [Upload Ubuntu 16.04 ISO to DRP] *******************************************************************************
fatal: [localhost]: FAILED! => {"changed": true, "cmd": ["drpcli", "bootenvs", "uploadiso", "ubuntu-16.04-install"], "delta": "0:00:01.084806", "end": "2019-02-05 14:33:11.110485", "msg": "non-zero return code", "rc": 1, "start": "2019-02-05 14:33:10.025679", "stderr": "Error: BootEnv ubuntu-16.04-install already has all required ISO files", "stderr_lines": ["Error: BootEnv ubuntu-16.04-install already has all required ISO files"], "stdout": "", "stdout_lines": []}

The workaround is to manually delete the the .iso file from the dr-provision/tftp directory, and then re-run the installation. Need to handle such errors automatically.

[bo-quan]

One customer reported that when iso file was not uploaded successfully, the iso upload step reported success and moved forward. The iso file upload failure should be handled correctly.

[ramanavakka]

Here is the log for the above issue
Explode ISO: SHA256 bad. actual: 16afb1375372c57471ea5e29803a89a5a6bd1f6aabea2e5e34ac1ab7eb9786ac expected: c94de1cc2e10160f325eb54638a5b5aa38f181d60ee33dae9578d96d932ee5f8
frontend
bootenv.go:381
[14:50]
Authenticated user rocketskates from ::1