contrib/init: (OpenRC) Do not fail if both rpcuser and rpcpassword are unset.

This implies the .cookie file shall be used for RPC and having _both_ unset
in bitcoin.conf should allow bitcoind to start.

contrib/init/bitcoind.openrc

@@ -69,7 +69,8 @@ start_pre() {
 
 checkconfig()
 {
-	if ! grep -qs '^rpcpassword=' "${BITCOIND_CONFIGFILE}" ; then
+	if grep -qs '^rpcuser=' "${BITCOIND_CONFIGFILE}" && \
+		! grep -qs '^rpcpassword=' "${BITCOIND_CONFIGFILE}" ; then
 		eerror ""
 		eerror "ERROR: You must set a secure rpcpassword to run bitcoind."
 		eerror "The setting must appear in ${BITCOIND_CONFIGFILE}"