Use executor['timeout'] for timeout in ShellOut in executor.execute!

While writing and testing a wrapper cookbook for jenkins, I experienced convergence failures due to `jenkins_plugin` resources timing out. While simply setting `retries` to a non-zero value helped in many cases, it seemed like using the already defined `executor['timeout']` attribute made sense here rather than a hard coded 30 seconds. 

I did attempt to run the test kitchen tests and I believe anything relating to this code passes. Some are failing, but I think they are failing due to the open Jenkins bug affecting authentication since the failures occurred in the (misspelled) `smoke_package_lastest` suite.