net-test: packetdrill: config: fixed typos

Fixed typos in the 'usage' message: a few ']' were missing

Signed-off-by: Matthieu Baerts <matttbe@gmail.com>

gtests/net/packetdrill/config.c

@@ -103,9 +103,9 @@ void show_usage(void)
 		"\t[--local_ip=local_ip]\n"
 		"\t[--gateway_ip=gateway_ip]\n"
 		"\t[--netmask_ip=netmask_ip]\n"
-		"\t[--init_scripts=<comma separated filenames>\n"
-		"\t[--speed=<speed in Mbps>\n"
-		"\t[--mtu=<MTU in bytes>\n"
+		"\t[--init_scripts=<comma separated filenames>]\n"
+		"\t[--speed=<speed in Mbps>]\n"
+		"\t[--mtu=<MTU in bytes>]\n"
 		"\t[--tolerance_usecs=tolerance_usecs]\n"
 		"\t[--tcp_ts_tick_usecs=<microseconds per TCP TS val tick>]\n"
 		"\t[--non_fatal=<comma separated types: packet,syscall>]\n"