SpuriousSeedAnnihilator: fix a major in the synchronization code

The number of synced ranks needs to be set to 0 before telling the first
rank to proceed. Otherwise, this is a ugly race condition.

Maxime Boissonneault (Calcul Québec) helped me to launch Ray
with mpiexec without using the job scheduler directly
(option -x in mpiexec and absolute path).

This is the command I used to find the issue using:

$ cat launchers/template.sh-ERS006494.sh-256-Machines

module use /rap/nne-790-ab/modulefiles/
module load apps/ray/2.3.0-devel-90077789962a9615f367981f2fead96b905a9617

rm -rf ERS006494-256-CHECKPOINT-colosse-machines-1

start=$(which mpiexec)

$start \
-x PATH \
-x LD_LIBRARY_PATH \
-output-filename ERS006494-256-CHECKPOINT-colosse-machines-1 \
-n 256  \
-machinefile Machines.txt \
./Ray \
-k 31 -o ERS006494-256-CHECKPOINT-colosse-machines-1 \
-detect-sequence-files objects/ERS006494 \
-read-write-checkpoints ERS006494-GameSave.txt-2 \

Link: https://github.com/sebhtml/ray/issues/192
Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>