tests: Use en_US.UTF-8 locale for printf

This is required for floating point formatting, to make sure it uses dot
(`.`). Some languages (such as Romanian) use comma (`,`).

Signed-off-by: Razvan Deaconescu <razvan.deaconescu@upb.ro>

tests/run_all_tests.sh

@@ -38,6 +38,6 @@ total_grade=$( (echo "scale=0"; echo "$total / 10") | bc )
 echo ""
 echo -n "Total:                           "
 echo -n "                                "
-printf "%3d/100\n" "$total_grade"
+LC_ALL=en_US.UTF-8 printf "%3d/100\n" "$total_grade"
 
 rm results.txt