use mcr repos and disable smb flexvol addon

[jackfrancis]

What this PR does / why we need it: Compare to: Azure/acs-engine#4266

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

Special notes for your reviewer:

If applicable:

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

Release note:

use mcr repos and disable smb flexvol addon

[codecov]

Codecov Report

Merging #45 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #45   +/-   ##
=======================================
  Coverage   52.41%   52.41%           
=======================================
  Files          91       91           
  Lines       12792    12792           
=======================================
  Hits         6705     6705           
  Misses       5479     5479           
  Partials      608      608

[tariq1890]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis, tariq1890

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