Update find-duplicate-lines.sh

Make the code return an error code if a file ended with a duplicated line is founded.

tests-data/tools/find-duplicate-lines.sh

@@ -1,9 +1,12 @@
 find ./glances/ -type f -name "*.py" -exec sh -c '
+    duplicate_found=0
     for file; do
         last_line=$(tail -n 1 "$file")
         second_last_line=$(tail -n 2 "$file" | head -n 1)
         if [ -n "$last_line" ] && [ -n "$second_last_line" ] && [ "$last_line" = "$second_last_line" ]; then
             echo "Duplicate last line in: $file"
+            duplicate_found=1
         fi
     done
+    exit $duplicate_found
 ' sh {} +