Implement HTTP POST based RPC (#5840)

Added support for new RPC support using HTTP POST.  RPC's 
arguments and reply are Gob encoded and sent as HTTP 
request/response body.

This patch also removes Go RPC based implementation.

cmd/http/timeoutconn.go

@@ -0,0 +1,62 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package http
+
+import (
+	"net"
+	"time"
+)
+
+// TimeoutConn - is wrapped net.Conn with read/write timeouts.
+type TimeoutConn struct {
+	QuirkConn
+	readTimeout  time.Duration
+	writeTimeout time.Duration
+}
+
+func (c *TimeoutConn) setReadTimeout() {
+	if c.readTimeout != 0 && c.canSetReadDeadline() {
+		c.SetReadDeadline(time.Now().UTC().Add(c.readTimeout))
+	}
+}
+
+func (c *TimeoutConn) setWriteTimeout() {
+	if c.writeTimeout != 0 {
+		c.SetWriteDeadline(time.Now().UTC().Add(c.writeTimeout))
+	}
+}
+
+// Read - reads data from the connection with timeout.
+func (c *TimeoutConn) Read(b []byte) (n int, err error) {
+	c.setReadTimeout()
+	return c.Conn.Read(b)
+}
+
+// Write - writes data to the connection with timeout.
+func (c *TimeoutConn) Write(b []byte) (n int, err error) {
+	c.setWriteTimeout()
+	return c.Conn.Write(b)
+}
+
+// NewTimeoutConn - creates a new timeout connection.
+func NewTimeoutConn(c net.Conn, readTimeout, writeTimeout time.Duration) *TimeoutConn {
+	return &TimeoutConn{
+		QuirkConn:    QuirkConn{Conn: c},
+		readTimeout:  readTimeout,
+		writeTimeout: writeTimeout,
+	}
+}