deploy needs to provide live output from ovftool, handle user prompts

[glennmatthews]

Currently cot deploy has two major limitations in its handling of ovftool:

1. It caches all output from ovftool while the tool runs and only dumps the output to screen after ovftool exits. Since ovftool can take a while to run, it's not clear to the user what is happening during this time.
2. In some cases ovftool may prompt the user for input mid-run, such as:

The manifest validates

Accept SSL fingerprint (71:80:F5:C1:F1:41:41:38:11:90:2C:1D:F4:11:75:19:35:AF:94:21) for host 192.1.1.4 as target type.

Fingerprint will be added to the known host file

Write 'yes' or 'no'

Because of item 1) above this prompt will not be displayed to the user and so COT will hang indefinitely.

Solution:

1. COT needs to provide live output from ovftool as it runs
2. COT needs to pass prompts for user input from ovftool through to the user, or automatically handle the prompts as appropriate.