Implement compatMode raw JSON output and fix tls_verify init on pull()

[D3vil0p3r]

Fix #492

Added compatMode param to pull() function. Default as True in order to give a detailed progress JSON output by default like:

...
{'status': 'Pulling fs layer', 'progressDetail': {}, 'id': 'ef3afbc03436'}
{'status': 'Downloading', 'progressDetail': {'current': 1862903, 'total': 37308955}, 'progress': '[==>                                                ]  1.863MB/37.31MB', 'id': '1546de61b6c3'}
{'status': 'Download complete', 'progressDetail': {}, 'id': 'fa424c11eb04'}
{'status': 'Pulling fs layer', 'progressDetail': {}, 'id': '3d3d38ab8766'}
{'status': 'Downloading', 'progressDetail': {'current': 1441042, 'total': 3248294}, 'progress': '[======================>                            ]  1.441MB/3.248MB', 'id': 'ef3afbc03436'}
...

while compatMode=False still keeps the one-field stream JSON output:

{'stream': 'Copying blob sha256:30babffc8f090f7c78c263b9a1b683b34ca5f73da74911ffe942d4d8225dca57\n'}

This approach differs from the already present progress_bar=True because does not show the "fancy" progress bar but a raw detailed progressing JSON output, useful for devs want to manipulate pull output.

Furthermore, the PR fixes tls_verify initialization in pull() because, according to its description, its Default should be True, but it was actually as None.

[D3vil0p3r]

/retest

[openshift-ci]

@D3vil0p3r: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[D3vil0p3r]

@rhatdan I hope you are well. When you have free time, could you please give a quick check? "Test on Fedora" is failing because it cannot find the Alpine image, so, looking on its logs, I think it is an error not related to the PR.

[rhatdan]

Thanks @D3vil0p3r
LGTM
/approve
@jwhonce @umohnani8 PTAL

[openshift-ci]

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[umohnani8]

Changes LGTM
Just wondering if changing the default value of tlsVerify would cause current workloads to break. I agree that the default should be fixed, but need to ensure we don't break existing environments. @jwhonce wdyt?