tests: Use proper word splitting when executing tests

Use the shell special variable "$@" instead of the inferior $* to
execute the test command in ts_valgrind.  The expansion of "$@" respects
proper word splitting and makes it possible to pass the command empty
arguments.  It might also prevent surprises with quoting in corner
cases.

Tested that `make check` passes.

Valgrind run with `make check TS_OPTS='--nonroot --memcheck'` passes.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>

tests/functions.sh

@@ -367,11 +367,11 @@ function ts_init_py {
 
 function ts_valgrind {
 	if [ -z "$TS_VALGRIND_CMD" ]; then
-		$*
+		"$@"
 	else
 		$TS_VALGRIND_CMD --tool=memcheck --leak-check=full \
 				 --leak-resolution=high --num-callers=20 \
-				 --log-file="$TS_VGDUMP" $*
+				 --log-file="$TS_VGDUMP" "$@"
 	fi
 }