Removed is_snappy function

[larohra]

Removed is_snappy function from version.py as Snappy Ubuntu core has its own /etc/os-release file now which is recognised by python's platform.dist() that we use to determine the OS of a VM

Description

Issue #

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• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
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This change is 

[codecov]

Codecov Report

Merging #1774 into develop will increase coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1774      +/-   ##
===========================================
+ Coverage    68.66%   68.69%   +0.02%     
===========================================
  Files           82       82              
  Lines        11737    11729       -8     
  Branches      1645     1642       -3     
===========================================
- Hits          8059     8057       -2     
+ Misses        3326     3322       -4     
+ Partials       352      350       -2

Impacted Files	Coverage Δ
azurelinuxagent/common/version.py	71.73% <ø> (+2.56%)	⬆️

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