As part of T25, I need to access the list of inflight systemd ops. In order to reduce code duplication, it would be nice to convert the list of inflight ops to a hash table. The key would be the unit name and the value would be the svc_action_t. This would allow getting rid of (or reducing) the services__systemd_get_inflight_op function.

And while we're at it, we should just do the same thing to blocked ops. There's no need to do so at the moment, but it would basically be the same code.