ci.jpl: Initialize "output" variable

Otherwise it's possible to get error like:

groovy.lang.MissingPropertyException: No such property: output for class: groovy.lang.Binding

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I83f7cfd350d111b2c8cc362904a4694be84ce923
1 file changed