System web server test: wait until exactly one Passenger instance exists
System web server test: wait until exactly one Passenger instance exists

Apache restarts Passenger during Apache startup, so there are temporarily
two Passenger instances. This will cause commands like 'passenger-status'
to fail. So we wait until the first instance has exited and the second
instance has fully initialized.

phusion/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation,phusion/passenger_apt_automation