MB-7522 Fix race condition in test

Ensure we don't use the PID of the old, dead, view
group process (we're racing with couch_set_view).

Change-Id: Ifa1c68e88c61a93a3565585523a407a220d74d09
Reviewed-on: http://review.couchbase.org/23895
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>