update version to 2.1.6 (Azure#362)

* update version to 2.1.6

* fix unit test

update agent version to 2.1.5.2 for pre-release testing (Azure#359)

Merge pull request Azure#328 from hglkrijger/master

update agent to 2.1.5

Merge pull request Azure#321 from brendandixon/enable

Improved tracking successful agent enablement and fix Azure#319

update the agent version to 2.1.5.rc6 (Azure#318)

Increment RC and ensure running agent is not deleted (Azure#312)

Signed-off-by: Brendan Dixon <[email protected]>

update agent version to 2.1.5.rc4 (Azure#302)

update the agent version to 2.1.5.rc3 (Azure#286)

Update version to 2.1.5.rc2 (Azure#273)

* update agent version to 2.1.5.rc1

Remove unused import