Improve logging of process signalling.
Improve logging of process signalling.

[#89972162]

Signed-off-by: Glyn Normington <94963367bb5bbf046ec526f1d42ce35228051963@pivotal.io>

savaki/garden,tangfeixiong/garden,savaki/garden,cloudfoundry-incubator/garden,tangfeixiong/garden,cloudfoundry-incubator/garden