Passing sequence number to all Extension Commands

[larohra]

Description

This PR is to address the behavior where the Guest Agent is supposed to pass the latest Sequence number from the goalstate to all extension commands

Issue #

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PR information

• The title of the PR is clear and informative.
• 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.
• Except for special cases involving multiple contributors, the PR is started from a fork of the main repository, not a branch.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made and Travis.CI is passing.

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

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This change is 

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@9687794). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             develop   #1640   +/-   ##
=========================================
  Coverage           ?   66.7%           
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  Files              ?      78           
  Lines              ?   11233           
  Branches           ?    1577           
=========================================
  Hits               ?    7493           
  Misses             ?    3412           
  Partials           ?     328

Impacted Files	Coverage Δ
azurelinuxagent/ga/exthandlers.py	82.73% <100%> (ø)

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[pgombar]

LGTM