rhc ssh looks in wrong place for ssh executable

[jsvgoncalves]

From @otbster at openshift-cs/devcenter#376

On my windows git installation (version 2.6.2), "ssh.exe" is located at "C:\Program Files\Git\usr\bin". However the rhc ssh command only checks "C:\Program Files\Git\ssh.exe" and "C:\Program Files\Git\bin\ssh.exe", so does not find it.

Adding "#{base}\Git\usr\bin\ssh.exe" to the array in 441-452 of ssh_helpers.rb fixes the problem, on rhc version 1.37.1. (this is where rhc ssh creates the paths to check for ssh)