strongswan: check return value instead of output

When the strongswan service is running, `ipsec status` returns 0. Check
the return value instead of checking its output.

While at it, remove the [[ ]] bashism, use rereadall instead of
(reread)secrets, and move it inside the if statement.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

net/strongswan/files/ipsec.init

@@ -331,8 +331,8 @@ restart() {
 
 reload() {
 	prepare_env
-	ipsec secrets
-	if [[ ! -z "$(ipsec status)" ]]; then
+	if ipsec status > /dev/null 2>&1; then
+		ipsec rereadall
 		ipsec reload
 	else
 		ipsec start