using *zip*/archive.zip as default for :jenkins_artifact_file

deploy fails with `SSHKit::Runner::ExecuteError: Exception while executing on host <deploy host>: can't convert nil into String` when `:jenkins_artifact_file` not specified

using `*zip*/archive.zip` as default value

if `:jenkins_artifact_file` option not specified - unzipping artifact content and moving to release path.
This could be written like so (similar to the original line being replaced by this code block):

`context.execute :cp, downloaded_artifact, release_path`