tests/client-server.scm: Use `dynamic-wind'

* tests/client-server.scm: Use `dynamic-wind' for child processes in
  tests.
tests/client-server.scm (run-server-and-client): New procedure

* tests/client-server.scm (run-server-and-client): New procedure.
  ("connect!, disconnect!")
  ("get-protocol-version", "authenticate-server, not-known")
  ("authenticate-server, ok", "get-public-key-hash")
  ("userauth-none!, success", "userauth-none!, denied")
  ("userauth-none!, partial", "userauth-password!, success")
  ("userauth-password!, denied", "userauth-password!, partial")
  ("userauth-public-key!, success", "userauth-get-list")
  ("make-channel", "channel-get-session", "channel-open-session")
  ("channel-request-exec", "data transferring, string")
  ("data transferring, bytevector"): Use it.
tests/server-client.scm: Use `dynamic-wind'

* tests/server-client.scm: Use `dynamic-wind' for child processes in
  tests.
  (run-server-test): New procedure.
  ("accept, key exchange", "server-message-get", "message-get-type")
  ("message-get-session"): Use it.
tests/client-server.scm (run-server-and-client): Rename

* tests/client-server.scm (run-server-and-client): Rename to
  `run-client-test'.  All callers updated.
tests/server-client.scm ("accept, key exchange"): Add missed paren