forward the SSH_AUTH_SOCK in Go client

[unthought]

Fixes #845

Proposed changes

• forward the ssh agent socket found at SSH_AUTH_SOCK (if set) to remote, during okteto up and okteto exec.
• currently if the SSH_AUTH_SOCK env var is set, it's forwarded unconditionally. We might want to allow the user to disable this.

[derek]

Thank you for your contribution. I've just checked and your commit doesn't appear to be signed-off. That's something we need before your Pull Request can be merged. Please see our contributing guide.
Tip: if you only have one commit so far then run: git commit --amend --signoff and then git push --force.

[codecov]

Codecov Report

Merging #848 into master will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #848      +/-   ##
==========================================
- Coverage   33.12%   33.07%   -0.06%     
==========================================
  Files          67       67              
  Lines        5217     5225       +8     
==========================================
  Hits         1728     1728              
- Misses       3346     3354       +8     
  Partials      143      143              

Impacted Files	Coverage Δ
pkg/ssh/exec.go	0.00% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7f649fd...0ceaf27. Read the comment docs.

[rberrelleza]

Looks good to me, added couple of comments on changes I think should be done.

[pchico83]

Awesome contribution. Thanks @unthought!