try apply proxy only when proxy configured.

bump agent version to 2.122.0

support client certificate in agent.

2.120.2

m121 vstsom (microsoft#1116)

Added capability to detect the sql package in VS 17 (microsoft#1098)

* Added capability to detect the sql package in VS 17

* updated the logic with vswhere

bump agent version for tfs2017u2RTM. (microsoft#1051)

skip docker check. (microsoft#1021)

* skip docker check.

* bump version to 2.119.1

update agent version to 2.119.0