log errors in DCOS e2e test

[CecileRobertMichon]

What this PR does / why we need it:

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #3080

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• documentation
• unit tests
• tested backward compatibility (ie. deploy with previous version, upgrade with this branch)

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[codecov]

Codecov Report

Merging #3081 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #3081   +/-   ##
======================================
  Coverage    51.5%   51.5%           
======================================
  Files          99      99           
  Lines       15036   15036           
======================================
  Hits         7744    7744           
  Misses       6582    6582           
  Partials      710     710

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[dmitsh]

The error message of type "Error trying to install dcos client:Process exited with status 1" is not helpful. We need the actual error message produced by dcos.

[CecileRobertMichon]

@dmitsh the next line shows the exact error:

2018/05/25 20:43:38 Error while trying dcos cluster setup:Process exited with status 1
2018/05/25 20:43:38 Output:URL [http://localhost:80/pkgpanda/active.buildinfo.full.json] is unreachable.

[dmitsh]

Thanks, missed that line.
I think we need to increase the VM size in the cluster. I will send out another PR

[dmitsh]

@CecileRobertMichon are you considering merging this PR?

[CecileRobertMichon]

@dmitsh sure, can I get your review?