Fix INFO_ARG parsing

In split buffer conditions, a buffer is used to accumulate bytes.
After processing, this buffer needs to be reset.

Resolves #270

server/parser.go

@@ -540,6 +540,7 @@ func (c *client) parse(buf []byte) error {
 				var arg []byte
 				if c.argBuf != nil {
 					arg = c.argBuf
+					c.argBuf = nil
 				} else {
 					arg = buf[c.as : i-c.drop]
 				}

server/split_test.go

@@ -314,7 +314,7 @@ func TestSplitDanglingArgBuf(t *testing.T) {
 	c.parse(pubop[:22])
 	c.parse(pubop[22:25])
 	if c.argBuf == nil {
-		t.Fatal("Expected a nil argBuf!")
+		t.Fatal("Expected a non-nil argBuf!")
 	}
 	c.parse(pubop[25:])
 	if c.argBuf != nil {
@@ -337,6 +337,14 @@ func TestSplitDanglingArgBuf(t *testing.T) {
 	if c.argBuf != nil {
 		t.Fatalf("Expected c.argBuf to be nil: %q\n", c.argBuf)
 	}
+
+	// INFO_ARG
+	infoop := []byte("INFO {\"server_id\":\"id\"}\r\n")
+	c.parse(infoop[:8])
+	c.parse(infoop[8:])
+	if c.argBuf != nil {
+		t.Fatalf("Expected c.argBuf to be nil: %q\n", c.argBuf)
+	}
 }
 
 func TestSplitMsgArg(t *testing.T) {