Build on server behind proxy fails due to curl

[rameshsanth]

Build failure seen when building in a server that requires Proxy to access internet

Steps to reproduce the issue:

1. do make

Describe the results you received:

Step 20/24 : RUN curl -fsSL https://download.docker.com/linux/debian/gpg | sudo apt-key add -
---> Running in 5da854896cec
curl: (35) Unknown SSL protocol error in connection to xxxxx.com:8080
Warning: apt-key output should not be parsed (stdout is not a terminal)
gpg: no valid OpenPGP data found.
The command '/bin/sh -c curl -fsSL https://download.docker.com/linux/debian/gpg | sudo apt-key add -' returned a non-zero code: 2

Describe the results you expected:
No build error