Flush file system buffers before checking instance store setup

Signed-off-by: Luca Carrogu <carrogu@amazon.com>

Author: lukeseawalker

recipes/tests.rb

@@ -367,6 +367,8 @@ module load intelmpi && mpirun --help | grep '#{node['cluster']['intelmpi']['kit
       set -e
 
       if [ $NUM_DEVS -gt 0 ]; then
+        # flush file system buffers
+        sync && sleep 1
         mkdir -p ${EPHEMERAL_DIR}/test_dir
         touch ${EPHEMERAL_DIR}/test_dir/test_file
       fi