RFC: Refactor the remote_node module

Remove the extra 10 second sleep, which was called even before any
contact with the remote node was attempted, see [1]. So if node is up, the
response is immediate.

Also make sure that the TCPSocket is closed after check,
preventing the leak of file descriptors.

[1] https://github.com/crowbar/barclamp-crowbar/blob/release/roxy/master/crowbar_framework/lib/remote_node.rb#L7