Bug#842721: jayway-jsonpath: FTBFS (Could not resolve all dependencies)

[殷啟聰]

I tried the build and seems it is. The new gradle-debian-helper
automatically adds the "maven" plugin to every projects that has a
"java" plugin applied, and the "maven" plugin adds a "install" task
which seems to depend on the "jar" task. d/rules executes the
"install" task, which also executes the one of the test project.