Add missing initializer for show_json option.

4 jobs for fix-show_json-init in 119 minutes and 6 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #18984
build
fork_packages_deb9

01:02:16

passed #18967
build
fork_packages_el6

00:37:27

passed #18968
build
fork_packages_el7

00:56:49

failed #18969
build
fork_packages_deb9

02:00:04