Log Message:
Update ruby-net-ssh to 4.2.0.

=== 4.2.0.rc2

 * Fix double close bug on auth failure (or ruby 2.2 or earlier) [#538]

=== 4.2.0.rc1

 * Improved logging with proxy command [Dmitriy Ivliev, #530]
 * Close transport on proxy error [adamruzicka, #526]
 * Support multiple identity files [Kimura Masayuki, #528]
 * Move `none` cipher to end of cipher list [Brian Cain, #525]
 * Deprecate `:paranoid` in favor of `:verify_host_key` [Jared Beck, #524]
 * Support Multile Include ssh config files [Kasumi Hanazuki, #516]
 * Support Relative path in ssh confif files [Akinori MUSHA, #510]
 * add direct-streamlocal@openssh.com support in Forward class [Harald Sitter, #502]