Add a functional test case for SSH2 login using Agent.
Setup SSH key and agent for travis user.
Merge pull request #552 from bantu/ssh2-agent-login-test

SSH2 Agent Login Test

* bantu/ssh2-agent-login-test:
  Setup SSH key and agent for travis user.
  Add a functional test case for SSH2 login using Agent.
Merge branch 'master' into php5

* master:
  Setup SSH key and agent for travis user.
  Add a functional test case for SSH2 login using Agent.