[systemd] use LoadUnit instead of GetUnit

GetUnit fails when unit file is not loaded from disk. I believe this
fixes a bug when daemon couldn't be started from settings applet after
package update.
[Sailfish UI] use busy state on reporterSwitch when reporter is starting

When crash reporter launches for the first time after reboot, there is
30 seconds delay period before the service appears on D-Bus and starts
doing anything, in order not to slow down system startup with upload of
accumulated reports.

When this first startup was done via settings applet, there used to be
a long interim between tapping the switch and the bullet lighting up,
which might have been confusing for the user. Now the bullet blinks
during the daemon's activating period, giving an immediate feedback.
[systemd] cache service state

Spares some unnecessary D-Bus calls.
Incremented version