tvheadend: fix undefined variable in error print

The variable "$SCRIPTNAME" is undefined; replace with "$0".

Also, fix "Stopping" spelling.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>