Improve use of systemd's states
A better handling of systemd state is need to treat
correctly transient states. That change includes:
- Management of states with numeric identifiers
instead of names
- Handling of the state "inactive" as a stable
state. Most of previous seen problems were coming
from that miss.
- Returning no error but also no info on the process
if it falled to "inactive" meaning that it stopped
quickly.
Bug-AGL: SPEC-3323
Change-Id: Ibf35eb6257c5583596d675cad0bec2869f5fd5f7
Signed-off-by: José Bollo <jose.bollo@iot.bzh>