Retire also the reference to VSM_NOPID in docs
Retire also the reference to VSM_NOPID in docs

Ref previous commit to remove the use of kill(signull) on the pids of the
Varnish processes to test liveness.

gquintard/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache