Add support for env variables with SFTP client.

[di-ov]

This relates to and closes this issue: #1433

I basically saw how this was implemented in the exec() method in client.js and did a similar implementation.

I seems that it might be better to add an additional parameter to the sftp() method, i.e. in client.js it would appear as sftp(env, cb), I wasn't entirely sure, what do you think? Thanks!

[angelparaskov]

@mscdex we also would like to have such a solution.
May we expedite this one please?
Thanks

[mscdex]

I seems that it might be better to add an additional parameter to the sftp() method, i.e. in client.js it would appear as sftp(env, cb)

That would be the preferred approach.

[di-ov]

@mscdex thanks for the help, I did the changes. If it looks okay, I'll have a look at updating the docs.

[mscdex]

All that's needed now is a unit test. You'll probably have to use one similar to the last one in the SFTP test script to verify the environment is being sent properly before starting the subsystem.

[di-ov]

@mscdex so this look okay right? Would you be able to include it in the next release?