shellcheck: Fix shellcheck SC2145

> Argument mixes string and array. Use * or separate argument.

- Swap echos for printfs and improve formatting
- Replace $@ with $*
- Split arrays into separate arguments

Signed-off-by: stevenhorsman <steven@uk.ibm.com>

tests/stability/scability_test.sh

@@ -30,7 +30,7 @@ EOF
 function main() {
 	# Verify enough arguments
 	if [ $# != 2 ]; then
-		echo >&2 "error: Not enough arguments [$@]"
+		echo >&2 "error: Not enough arguments [$*]"
 		help
 		exit 1
 	fi