Add ssh_command option '--[no-]host-key-verify' when not paranoid.

Very much "inspired" by chefs ssh-command
Adding tests for ssh option --no-host-key-verify
paranoid comment
--no-key-host-verify option also for ssh_args (used by rsync).
ssh_args test
--host-key-verify compare for false instead of nil
Merge pull request #274 from teyrow/add_ssh_option_host_key_verify

Add ssh option --[no-]host-key-verify