tests: Add some debugging output for the test scripts themselves

The DEBUG option for tests/run enables debugging options to passt/pasta,
however that doesn't help with debugging the test scripts themselves, which
are fairly fragile.

Extend the DEBUG option so it also prints information on each command in
the test scripts to make it easier to work out where things are falling
over.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

test/lib/test

@@ -89,6 +89,8 @@ test_iperf3() {
 test_one_line() {
 	__line="${1}"
 
+	[ ${DEBUG} -eq 1 ] && info DEBUG: "${__line}"
+
 	# Strip comments
 	__line="${__line%%#*}"