runner/resultgen: Fix subtest runtimes

Runtimes for single subtest are not included in results json object
after switching to socket communication. Make times for both subtests
and dynamic subtests when using comms.

v2: added GitLab issue number, added Petri to Cc (Kamil)
  reformat so it could be applied (Kamil)

Cc: Petri Latvala <adrinael@adrinael.net>
Fixes: 9d889fa6 ("runner: Use socket communications")
Closes: drm/igt-gpu-tools#132


Signed-off-by: Piotr Kira <piotr.kira@intel.com>
Signed-off-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>