Add DockerEngine feature flag

[CecileRobertMichon]

What this PR does / why we need it: Deployments w/ GPU nodes in sovereign clouds need to install docker-engine without VHD as Moby is not compatible w/ GPU and AKS VHD is not yet available in sovereign clouds.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #4261

Special notes for your reviewer:

If applicable:

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

Release note:

[codecov[bot]]

Codecov Report

Merging #4262 into master will increase coverage by 0.02%. The diff coverage is 75%.

@@            Coverage Diff             @@
##           master    #4262      +/-   ##
==========================================
+ Coverage   50.75%   50.77%   +0.02%     
==========================================
  Files         109      109              
  Lines       17053    17062       +9     
==========================================
+ Hits         8655     8664       +9     
- Misses       7614     7616       +2     
+ Partials      784      782       -2

[jackfrancis]

/lgtm

[jackfrancis]

/lgtm